obolella, subgenus geyp- - descriptions oe new species.

C\MRRIAN BRACHIOPODA: OBOLELLA, SUBGENUS GEYP-

TE\S: BRlAi OBOEUS, SUBGENUS WESTOMA; ^AVITH

DESCRIPTIONS OE NEW ^SPECIES.

Bv

^{Ciiaui.es I).}

^Walcott,

Hononu'D ^{Curator, D'lrhhm,,f}StrdllffrnjihirPaleontologi/.

TABLE OF CONTENTS.

OBOLELLA A>D NEW SUBGENUS

GLYl'TIAS.

Obolella mohergi, newspecies.

Oholdla linddromi,newspecies.

Obolella {gh/pthts)

fnwm

Linnarsson.

BICIA, A

NEW

(4ENUS OF

THE

OBOLID^.

BiciagemmaBillings,noteson.

Bkiatvlittearefii, newspecies.

OBOLUS, ADDITIONAL

NOTES

ON.

Obolusfmeneghini,new species.

Obolustetoire)isis, new^species.

Obolus?zoppi, newspecies.

LINGCI.ELLA, NEW SPECIES ANP NOTES (IX PREVIOUSLY DESCKIBED ^SPECIES.

0. (L.) belhisWalcott, noteson.

0. (L.)boruemawd, new^species.

0. {L.)bicensis, new^species.

0. {L.) linnarssoni,new^species.

0. (i.)randomenm,new^species.

0. (L.) lichucherti, newspecies.

0. (L.) siemiradzkii,newspecies:

O. (L.) v'nionn var. convexns, newvariety.

WESTONIA, NEW SUBCJENUS OF OHOI.US.

O. {LirigulejMs) gregwaMatthew, noteson.

ACHITIS, NEW SPECIES OF 0. (.-ler(7/.sf) riigaliiK, news])ecies.

CAMBKIAN BKACHIOPODS OF

^SARDINIA.

Proceedings U.S. National Museum,Vol. XXlll— 1229 669

670 PROCEEDINGS OF THE NATIONAL MUSEUM.

In continuation of the study of the

Cambrian

Brachiopoda^' the fol-

lowing notes have been assembled,which

may

beof service tostudents prior to the publication of a monoofraph on the subject:

Genus OBOLELLA

Billings, 1861.

1861. Ohohlla Billings, Pamphlet,andGeologyofVermont, II, p. 946, fig. 346.

1861. OholellaBillings, Geol. Surv. Canada; Palfeozoic Fossils, I,p. 7,'fig!7.

1862. Oholdla

Meek

and Hayden, Proc. Acad. Nat. Sci. Phila., XIII,p.^4':3.5.

1863. OholellaHall,Sixteenth Rept. N. Y. State Cab. Nat.Hist.,p.133'pi vi fia^

17-21. ^{'i • '} ^•

1865. OhoMla

Meek

and Haydex, Smithsonian Contl). Xo. 172,Palfeontology UpperMi.'isouri, pp. 3, 4.

1866. OhoMlaDavidson, British SilurianBrachiopoda, |). 60.

1867. OholellaHall, Trans. AlbanyInst.,V, p. 108.

1870. OholellaDall, Am. Jour. Conchology, VI, pp. 162-164.

1871. OholellaBillings, CanadianNaturalistandGeologist, newser VI v. -^7

figs. 5, 6.

'

.1 -

,

1872. OholellaBillings,AmericanJournalof Science,3dser..Ill, p.3.55, figs.5 7.

1876. OholellaBillings, AmericanJournalof Science, 3dser., XI, p. l'76r 1881. Oholella Ford,AmericanJournalof Science, 3dser., XXI, p. 131.

1884. Oholella? Walcott, Monograph U. S. Geol. Survey, VIII, Pahf^ontologv EurekaDistrict, pp. 67,68.

1886. OholellaWalcott, Bulletin U. S.Geol. Survey, No. 30, pp. 109-119.

1889. OholellaWalcott, Proc. IT. S. NationalMuseum,XII, p. 36.

1892. Oholella HallandClarke,Pal.

New

York,YIII, Pt. _1, pp. 66, 164.

1892. OholellaMatthew,Trans. Roy.Soc. Canada, IX, p. 39.

1894. OholellaHallandClarke, EleventhAnnual Report

New

YorkStateGeol- ogist, p. 240, pi. Ill,figs. 5, 6, 7.

1896. Oholella Mickwitz, Mem. Acad. Imp. Sci. St. Petersbourg, VIII, _p. 116.

Generic c/iaracters.—SheU subequivalve, moderatel}- convex; dorsal valve

more

elevated at the

umbo

thanthe ventral; lonoitudinally ovate or oval in outline, with the dorsal valve sometimes transverselyoval.

Surface

marked

by concentric striw of

growth

and radiating* strite.

exceptinthesubgenus 0. {Gh/2)tias)

farom.

which hasirregula'i-trans- verselines crossing the concentric striae

Shell substance

unknown

in an unaltered condition; itappears to have been calcareo-corneous, as in Obolus. Shell structure

formed

of athin outer layerwith

many

thin inner layers or lamella-

more

orle.s.s

oblique to the outerlayer; the shortlameflteof the anterior portion of the valves are

more

oblique than the longer lamella of the_centraland

iNote onthegenusLingulepis: Am.Jour.Sci.,4thser..Ill, 1897, pp. 404, 405.

Cambrian Bi-achi.jpoda: genera Iphidea and Yorkia, with descriptions of new

species of each,and of the genus Acrothele: Proc. U.S.Nat. AIus

XIX

^{1897 nn}

707-718.

' ' -,. ^ . ..<, PI.

Note onthebrachiopod _fauna of thequartziticpebblesof the Carboniferous con- glomerates of the Narragansett Basin, RhodeIsland: Am.Jour. Sci. 4th ser VI

1898,pp.327, 328.

' -^'' ^-i'

CambrianBrachiopoda: Obolus and Lingulella, with description _of newsnecies- Proc.U.S. Nat.Mas.,XXI, 1898,pp. 385-420.

NO.1229.

CAMBRIAN BRACHIOPODA—WALCOTT. 671

po.steriorportions andlio on the odjifosin tho

samo

pianoa.sthoniaro;ins of thevalve.s.

Area

ofthe ventral valve rises

from

the phuu^ of themarginsof the valve at anglesvarying

from

^{10^}to 70^; broadly subtriangular

when

the beak is projecting, otherwise rounded at the posteiior margin almost as

much

as thearea of the dorsal valve; the latteris usuallyon the planeof themargins of thevalve andbroadlyroundedposteriorly;

both areas are striated parallel to the base

and

divided

midway

diti'er- ently in each valve and in an unusual manner; in the ventral valve a sharp, narrowpedicleslit cuts through the area

from

its base to the apex; this slit opens into acylindro-conical chamber, var3'ing in size

and form, that terminates in tho shellsubstance of the beak but does not penetrate to the surface of the shell; the stride of the area pass into the slit and encircle the pedicle chamber; the latter is in

form

similar to the pedicle tube of the Siphonatrotidte, except that it is closed at the outer end, and the pedicle obtained egress through the narrowslit in the area; the area of the dorsal valve is divided

by

a narrow, raised, triangular space that ^is bordered on either side

by

a

more

orless deeply impressed groove

formed

b}' a

narrow

fold of the areal lamella?; outside of this groove, and between it and the outer Hexure fold of the area, occurs a depressed triangular spacethat has' ))een considered l)y authors as thescar of tho pointof attachmentof cardinal muscles.

Sometimes

the inner angleof the area of the ven- tral valve adjoining the pedicle slit projects forward so as to

form

a tooth-like knob,whichinthe cast is

shown by

adeepindentation beside the cast of the pedicle

chamber

and betweenthelatterandtheproject- ing castof the undercut beneath the area.

Splanchnoccele' of the ventral valve contined to the posterior half, while in the dorsal valve it extends forward to and in

some

instances

beyond

thecenter; in bothvalvesitextends backtothesplanchnocoele part of the area, which is

bounded by

the tlexure lines. Traces of a median

septum

are

shown

inthe dorsal valve,butnodetinite

septum

has beenobserved intho ventralvalve.

A

^centralmedianridge ofvarying degree of sizeand length often extends towardthe central portion of the dorsalvalve;

when

^{it is} large adeep,rounded grooveusually occurs on each side of it, on the inner slope ofwhich the centralmuscle scars

may

^l)e situated. Often themedian ridgeis practically al)sont.

The

grooves of the

main

vascularsinuses begin in each valve at the front margin of thearea nearthe median lino,and in theventralvalve gradually extend forward and outward toward the front half of the shell,

where

they begin to gently curve inward, terminating toward the front of the valve, the distanceand curvature varying in ditferent species. In thedorsal valve tho

main

vascular sinuses curve out

more

rapidly, and are

much

less prominent; none of the secondary radial canals or the peripheral vascular sinuses have been observed.

The

^Usins;nomenclatureof INIickwitz.

672 PROCEEDINGS OF THE NATIONAL MUSEUM.

course of the parietal sear between the

main

vascular sinuses is in front of thesplanchnocwlein the Aentralvalve; also inthe

same

valves

it passesaround the muscle scars between the

main

_{sinuses and the} base of the area, in line with theflexure lineof thearea; in thedorsal valve it closely follows the outside limits of the muscle scars, butit

has not beentraced across the

main

vascular sinuses.

The

size andposition of the pediele and uml)onal muscle scarsare

unknown,

but theyare probablysimilar to those of Obolus.

The

cen- tral scars are placed alittledistance each side of the median line in the dorsal vahe. In the ventral valve they are not separable

from

themiddle and outside laterals,

which

occuron each side of the front of the visceral area.

The

middle and _{outside laterals of the dorsal} valve are blended and lie obliquelyoutward, _{before the} transmedian

scars.

The

transmedian scars areclose to the base of the areain both valves, and lie in the line of the prolongation of the flexure lineof thearea. In

number and

relative positionthemusclescarsof0]:)olena are essentially the

same

as those of Obolus.

Oh><ervatlons.—ThQ genus Obolella has been under discussion

by

authors for nearly fortyyears. In the original description :Mr. Bil- lings noted its resemblance to Obolus, but claimed that it isdistinct on account of the difference in

"the

arrangement of the muscular impressions." Later (187(3) he

compared

it again with Obolus, but having poorillustrations of both Obolus and Obolella ho failed todis- cover the trueposition

and

relations ofthe musclescars in either. _It

was

not until after Mickwitz's

memoir on

Obolus appeared,

and

the collectionsof Obolella

made

during the

summer

of 1899

were

studied, that any correctcomparisons couldbe made. It then

became

evident that there is practically

no

difference in the arrangement of the muscle scarsof the

two

genera, butthat there are

most

essential dif- ferences in the areas of the ventral valve. Before

working

_{out the}

relationsof the

narrow

pedicleslit of Obolella to the cylindro-conical pedicle chamber, I

was

at a loss to find generic differences ofvalue, althoughI felt thatthe area of the dorsal valve of Obolella indicated differences notreadily explained.

The

pedicle passage of Obolus varies greatly in size and form, l)ut it isalways an open furrow. In Obolella it is in the ventral valve a cylindro-conical inner

chamber

opening through _a

narrow

slit in the area of the ventral valve,the area rising

from

the plane of themargin of the valve; in the ventral valve a slightly raised area occupies the place of the broad furrow in Obolus.

Obolella is confined to the Olenellus or

Lower Cambrian

fauna.

Obolus, as

now

limited, appears in the Middle Cambrian, Inithas its

greatestdevelopment in the

Upper Cambrian

fauna.

Of

the subge- nera Oholiis {Lingidelhi) schuchertl is found associated with Obolus

(O. erassa) atTroy,

New

York.

Bkiagtinina

isassociated with Ololdla C7'<6y.s(cboth at

Bicand Trov

N0.12J9.

CAMBRIAX BRACHIOPODA—WALCOTT.

()73 andthe species

was

referred toObolella

by Mr.

Billings. Itdiffersso radically

from

Obolellain thecharacter ofthe areas of the valves and the interiormarkingsthat it isscared}^ necessaryto institutecompari- sonsbetweenthem.

01)olellaas

known

atpresentislimitedto sixspeciesand one variety:

Oholdla chromaiicaBillings".

Obolellaailant'tca"Walcott.

Obolellaa^issaHall.

Obolella crassa var. elonyata "Wak-ott.

.Obolellafavosa Linnarsson.

ObolellallndstrdmiWalcott.

ObolellamobergiWalcott.

Of

the above

two

species 0. chromatica

and

0. atlantieabelong to the

upper

portion of the Olenellus fauna,and 0. crassa andvar.elon- (jata to the lowerportion.

The

three Swedish species O.favosa^ O.

Jindstruinl, and O. inohergi are

from

the basal

Cambrian

sandstones and

may

belong tothe

same

horizon as 0. crassa.

The

species that have heretofore ])eenreferred to Obolella, inaddi- tiontothose listedabove, are noAV distributedin thefollowing genera:

?ambigua Walcott =Elkania.

0. cingidata Billings =Kutorgina.

0. circe Billings =Billingsella.

0. coelata Billings =Acrothele.

0. desquamataBillings

=

Obolellacrassa.

0. desiderata Billings =Elkania.

0. discoidea HallandWhitfield

=

Obelus(Lingulella).

0.gemma Billings =Bicia.

0.gemmula Matthew =:Obolns (Lingulella).

0. ida Billings =(?)

0. minuta HallandWhitlield=Acrotreta.

0. misera Billings =Linnarssonia.

0. nana - MeekandHayden=Dicellomus.

0. nitida Ford =Linnarssonia(?)

.

0.pectenoides Whitlield =Dicellomus.

0. polita Hall =Dicellomus.

0. pretiosa Billings =Linnarssonia.

0.prima AVhitfield =Obolus(Lingulepis).

0.transversa Hartt =Linnarssonia.

OBOLELLA MOBERGI,

new species.

General

form

^ovate, with the ventral valve subacuminate and the dorsalvalve obtuselysubacuminate; valves moderate!}' convex.

Beak

of the ventralvalve slightly elevated above the plane of the shell;

beak of the dorsal valve curved

down

to the planeof the margin.

Surface of theshell

marked by

concentric lines and stride of growth, and in

some

examples

by

ratherstrong, radiating,broken,and slightlj^

irregularraisedlines.

The

elevatedlines areof the

same

characteras thoseon Bicia

gemma. The

shell is

formed

of athin outer la3'er

and numerous

inner layers orlamellte, the latter overthe anterior half of

Proc. N. ^j\I. vol. xxiii 43

674 PROCEEDINGS OF THE NATIONAL MUSEUM

^vol.xxiii.

the shell. Theseinner lamelleeare obliquetothe outer layerand are arranged as imbricating'laj^ers, very

much

asin 0.favosa.

A

ventral valve 10

mm.

in length hasa width of 9

mm. A

dorsal valve 9

mm.

longhas the

same

width.

The

area of the ventral valve is of

medium

length and tippedl^ack of the edgeof the valveto

meet

the beak. It extends well out

on

to the cardinal slopes of the valve. It isdivided

midway

])ya

narrow

pedicle

furrow

that passes inward into a largecylindrical chamber, closedatitsouter end.

The

surface of the area is

marked

T)y rather strong transversestripecrossing the areaand extending in

and

around the pedicle slit

and

chamber.

On

each side of the pedicle

chamber

there is a rather strong undercutwhich in thecast is replaced

hy

a

marked

tooth-like projection.

The

area of the dorsal valve ^is

narrow

and, as far as can be determined

from

the single cast, ver}' nuich like that of 0. crassa.

The

castsof the interior of the ventral valves

show

a central visceral area, very

much

likethatin O. crassa; also

two

strongly

marked

vas- cular sinuses thatextendwell intothe middleof thevalve.

No

clearly defined nuiscle scars are

shown

on an}-of the specimens. Casts ofthe interior of the dorsalvalve give little satisfactorydatain relation to themuscle scars.

The

cast showsa part of the outline of the visceral area, alsothe impression of the transmcdian musclescar.

Ohservations.

—

^{This speciesappears to bethe}

^European

representa- tiveof 0. crassa,

which

occurs at the

same

relative stratigraphic hori- zon at Troy,

New

York.

The

Swedish species differs

from

the

American

in being^slightly

more

elongatein outlineand in having the interior thickenings of the area

more

strongly developed.

The

exte- riorsurface alsoappearsto be

marked by

stronger radiatinglines. It differs

from

O. atlantica and 0. chromatica in being a

nmch more

robust shell, and in

many

slight details. O. j>rlstinusis

more

rotund

and

convex.

O. onohergl is associated withthe Olenellusfaunain

Sweden

in the

Schmidt

latoreUizone.

Format

ionandlocallty

.

— ^Lower

^Caml)rian.

^Zone

^of

^Schmidt

^iator-

elli^ Bjorkelunda, south of Simrishamr, inagraysandstone. Sularp, near

Lund,

Sweden, in a

brown

sandstone.

Received

from

Dr. Joh. Chr. INIoberg.

OBOLELLA LINDSTROMI,

newspecies.

This speciesdiffers

from

Oholellamobergiⁱⁿthe

more

subacuminate outline of the valves, the surface characters,

and

the interior of the dorsalvalve.

The

surface of 0. lindstromiis

much

like that ofBicia

gemma.

The

ventral valve occurs ina hardgray sandstoneof the Schmidtia toreUi zone, and the castof the dorsal valveis

from

one of the

brown

NO.1229. CA

MBRL

¹

X BRA CHIOPODA— WA

LCOTT.

675

sandstone spots thatoccur within thegraysandstoneat Sulurp. I

am

not sure that the dorsal valveillustrated actuall}^ belong's to this spe- cies, as it is notassociated with the typicalventral valve.

It differs

from

thetypicaldorsal valves of O.moltergimbeing-

more

acuminate, and there is no correspondingventral valveassociatedwith

itinthe material studied.

I take pleasurein

naming

the species in honorof Dr.G. Lindstrom, to

whom

all paleontologists aredeeply indebted for his

many

contri- butions tothepaleontology of the Silurian formations of Scandinavia.

Fonnation and

locality.

— ^Lower

^Cambrian.

^Zone

^{of Schmidtia}

tordUi Bjorkelunda, south ofSimrishamr.inagraysandstone. Sularp, near

Lund,

Sweden, in a

brown

sandstone.

GLYPTIAS, newsubgenus.

The

subgenusGlyptias isbasedonthepeculiar surface sculpture

and

the veryshortarea.

Type.

—

Oholella i^Glyptlas)favosa Linnarsson.

OBOLELLA (GLYPTIAS) FAVOSA

Linnarsson.

Lingula_{?)favosa Linnarsson,Ofversigt afKongl.Yetenskai^s-Akad. Forhand- lingar, Ko. 3. Oin nagra forsteningar fran A'estergotlands sandstenslager, p. 356, 1869. Also the English translation,publishedasapamphlet,p. 16.

Stockholm, 1869.

General

form

ovate, with the ventral vah'e subacuminate and the dorsal valve obtuselyrounded; valvesmoderatelyconvex.

The

dorsal valveisabruptlycurve:^

downward

atthebeakto theplane of the edge of the shell, while the beak of the ventral valve is slightly al)ove the margin, the posterior edges of the shell curving

up

to

meet

it,

and

thus forming a passage for the pedicle out of a

narrow

pedicle

slit. Surfaceof theshell

marked by

verylineconcentric linesor stride ofgrowth,crossed transversely

by

undulating,slightl}' lamelloselines in almostidenticallythe

same manner

asin OTxdus(Wcstoalii)stoneanus of the

Upper Cambrian

of AYisconsin.

When

the outer surface of the shell is exfoliated or

worn

oft'

by

attrition, which is the usual condition, the surface of the inner laj^ers shows line, radiating, and concentric striaB.

The

shell is

formed

of a very thin, highl}" orna-

mented

outer layerand

numerous

inner la^'ersor lamellae; the latter overthe anterior portions are obliquetothe outerlayer,and

when

the shell is partially exfoliated they appear as imbricating layers, very

much

as in Obolusmatinalls.

The

largestventralvalvein the collection has a length of 7 nmi.and awidth of 6

mm. An

associateddorsal valve 6

mm.

long has awidth of 6.25

mm.

The

area of the ventral valve is

narrow and

rises slightl}^ to

meet

the beak,

which

iselevatedabove the posterior margin.

The

pedicle

676 PROCEEDINGS OF THE NATIONAL MUSEUM

^vol.xxiii.

furrowor slit is siiortand narrow, and, judging"

from

the appearance of the specimens,

where

the

beak

of thevalveis})roken

away

itopened intoa pedicle

chamber

that

was

closedat the outer end as in OhoJellu crassa and otherspecies of the genus.

On

the dorsal valve thereisno evidence of a true area except in thepresence of a narrow, thickened rim

somewhat

like that ofthe dorsal valve of B'tchi (jemma.

None

of the muscle scarsare

shown

in the ventralvalve.

The

position ofthe central

and

anterior lateral scars of the dorsal valveis indicated b}"

the outlineof thevisceral cavity.

Of

thevascularmarkingsthe

main

sinusesare clearly

shown

in each valve, alsotheoutline of theposition ofthe parietal scar.

Ohservatlons.

—

^This beautiful little shellhas remained without illus- tration since Dr. Linnarsson gave it a

name

in 1809, based on the

"singularsculpture'' of theouter shell. In a collection

made

for

me by M.

Schmalensee, the collectorof the Swedish Geological Surve}', there

were

several specimens

showing

casts of theinterior

more

or lessimperfectl3\

From

these I

was

able to ascertain that the shell

had the generic characters of Obolella, although differing

from

the typical species of thatgenus in the character of the surface ornamen-

tation.

The

outer surface hasbeenseenonl}^onthe posterior

umbonal

portion of the valves in the shellscollected for

me by M.

Schmalensee.

Formation and

locality.

— ^Lower

^{Cambrian. Fucoid sandstone.}

Vestergotland, Bithingen, Sweden.

Genus BICIA,

we^rv

genus.

Shell subequivalve, moderately convex; longitudinallv ovate, with the ventral valvesometimes subacuminate and the dorsal valve sub- circular. Beaks of both valvesas

now known

terminate atthe poste- riormargin. Surface

marked by

concentric and radiatingaivvx.

Shell substance

unknown

in anunalteredcondition. Shellstructure

formed

of a thin surface layerand

numerous

inner layers or lamellte

more

or less oblique to the outer layer.

Area

of the ventral valve usually on the plane of the edges of the valve, butin

some

instances rising at a lowangle; it isusually high,

and

triangularin outline, but the apex

may

be I'ounded and the basecurved forward at the

median

line; divided

midway by

a

narrow

pedicle furrow and again at each side

by

a

narrow

flexure line that extendsforward

and

outward

from

theapex.

Area

of dorsal valve^short, appearingin bothof the

known

species to rise

from

theplane of the edges of the valve. Strife of

growth

subparalleltothe base cross the areas.

The main

vascular sinuses of the ventral valve are

narrow

and extend forward

from

the projecting center of the base of the area, gradually separatingas they ^cross the visceralareaand extendingfor-

ward beyond

the transverse center of the shell; in the dorsal valve they appear toseparate

more

rapidlyand to follow the outer

margin

I

N0.1229.

CAMBBIAX BRACinOPODA—WALCOTT.

(577 of theventral cavity exceptin the second species.

A narrow

median

septum

is indicatedin the dorsalvalveon the crestofa strong median ridge.

One

of the striking features in both of the

known

species of this

genusis the oblong oval boss that is present in the ventral valve of mostadultshells. Itissituatedoneachsideof theforward projecting centralportion of the area, withthe largeraxisextendingforward and outward

when

the shellissubacuminateor transvers(^l_v Avhen the shell is broadly rounded. In the dorsal valve of Jj.

gemma

it is not so well defined as in

B.

whlttcivesL

The

boss is

bounded

b}^ the

margin

of thebase of thearea, the

narrow

elongate sulcus containing themar- ginal muscle scarsand the base of the

main

vascular sinuses. In

B.

v'Jiifeavesiit reached its greatest development in bothvalves, resem- bling in position and surface characters the posterior adductor scars of theCraniida?.

Somewhat

similarbosses occurin the ventral valve of Oholella crassaand OhoJasajMlI'tnis, but they are not developedto the extent they are in Bicia.

They

appear to occur only in those thick shells that have deposits of shell substance over the visceral area.

The

outline of the parietal scar in the ventral valveincloses a heart- shaped visceral area in the ventral valve, closelycircumscribing the muscle scars. Itsgeneral course in the dorsal valve is suggested

hy

the position of the musncle scars.

Fivepairs of muscle scars have been observed.

The

rather large central scars inthe dorsalvalve are placed close to thebroad

median

ridge, alittlebackof thecenter;the small anteriorlateralsareslightly in advance of the centrals on the median ridge, close to the

median

line; the transmedian scars arealmost underthe edgeof the areaand near the outer margin; the outside and middle lateralsare slightly in advance and further out than the transmedian scars; the centrals, middlelaterals, and outside laterals of the ventral valve are

grouped

inthe

narrow

space on each side of the U-shaped forward projecting portion of the visceral area. Traces of individual scars have been seen,but theycan notbe separated so as to identify them.

The

trans- median andanterior lateral scars are close to the outermargin of the valveand just inadvance of theoblong bossin frontand each side of the forward-projecting baseof the area.

Umbonal

andpedicle scars

unknown

except

what may

possibly be a small

umbonal

scar in the dorsalvalve of B. vJiiteaves't.

Type.

—

OholeUa geinma Billings; second species, Blcla tchlteavesi Walcott.

Ohsei'vations.-

—

^{Bicia isa}

^form

^{that combines}

many

of the character-

isticsofObolella

and

Obolus. Itresembles Obolellainthearrangement of the muscle scars

and main

vascular sinuses of the interiorof the valves. It differs in having a high area with an open pediclegroove

678 PROCEEDINGS OF THE NATIONAL MUSEUM

^vol.xxiii.

in the ventral vulve and anelevated ridge or boss in the back portion of the dorsal valve ^that in one species,

H.

icJuteavcKt^ appear to have

])een thebase of attachment of

some

portion of the muscular system.

The

ensemble of the dorsal valve of Bicia is unlike that of either Obolella orObolus. Bicia, withits thickshell,high area,deepcentral cavity (heart-shaped cavity of Mickwitz). arrangementof visceral cav- ity, musclescars, andvascularmarkings in the ventralvalve, is atrue Obolusofthe ().apoUlnistype,butⁱⁿits

more

elongateoutline,strongly striated surface, and in nearly all details of the dorsal valve it is quite distinct.

Of

the

two

species

now

referred to, the genus B. gcnnna has an unusually thick shell and a very

marked

deposit of shell substance overthevisceralarea in the ventralvalve,the posterior portion of the

same

area inthe dorsalvalve,and alongits

median

line. In thesecond species there is a considerable deposit over the

same

area with the exception of the median line,

where

the strong medianridge isabsent.

BICIA

GEMMA

^Billingssp.

fJhoJcUd(jemma Billings, Can. Xat., 1872, newser., VI, p. 218, fig. 5, p. 217.

OhoMlagemmaWalcott, Bull. U. S.Geol. Sur., Xo. 30, 1886, p. 116, pi. x, figs.

2,2a-e; Tenth Annual Report U. S.Geol. Sur., 1881, p. 612, pi. lxxi, figs.

5,5a-c;pi. lxxii, figs.2, 2a.

OhoMlagemmaHallandClarke,Pal.X.Y., 1892,VIII, Pt. I,pi. ii,figs.42-44.

General

form

ovate, with ventralvalve subacimiinate

when

thebeak

isextended orobtuselyacuminate

when

the beak is rounded; dorsal valve oval to subcircular in outline.

The

convexity of the valves is fairlystrongand nearlj^ the

same

in each

where

they are

embedded

in the

same

matrix.

Surface of shell

marked

1)y

numerous

slightly irregular concentric

strife and lines of growth;

by

line radiating strite between stronger radiating lines, and on

some

shells b}^ undulations of strongly devel- oped, elevated, radiating stria?; the radiating stria? are often slightly irregularand interrupted.

When

the outersitrface ispartiall}"

worn away

it issmooth, or the shellhas a peculiar surface

formed by

traces ofthe radiatingundulationsand stria?.

The

concentric stria? and lines of

growth

are

shown

on theouter surface of the inner laj^ersof the shell and on the interiorsurface,

where

rather strong radiatingstride

are often beautifully shown.

The

shellis usually thick and strong for one so small; those

from

St.

Simon and Troy

appear to becalcareous and

formed

of one solid layer. This is probablv

owing

to their condition of preservation,as inaweathered specimenlamellreobliquetotheouter surface areclearly shown,and indicationsof lamellaonthecentraland posterior portions thatpointtothe

same

shellstructure as in Obolusand Obolella.

The

ventral valves average about 5

mm.

in length; the largest is

N0.1229.

CAMBRTAN BRACHIOrnDA—WAIJOTr. 679

Timi). AVidth, averag-e, 4

mm.;

largest, 5

mm. The

dorsalvalve is

about one-iifth shorter than the ventral.

The

area of the ventral valve is usually on the plane of themargins of the valve, but

many

specimens

show

it rising ut angles varying

from

I'-'to^{10-^.} Itis high and narrow,

somewhat

as in Obolus{Lingu- MJ(i) acarninatusMickwitz, anddivided

midway

1)ya strong, rounded, narrowpedielofurrow; the stri»of

growth

are rather coarseand arch forward at the center and across the pedicle furrow, following the contourofthebase of thearea; thepositionof theflexurelineis some- times clearly

shown

b}' a narrowdepression.

The

areaof the dorsal valve isshort and easily escapes observation exceptin well-preserved shells. Itsometimeshas aslight central pedicle depression,andoften

is

onW

a short,almostsmoothsurfaceextendingwelloutonthecardinal slopes of the valve.

The

muscle scars, as far as determined, are arrangedas in Obolus.

The umbonal

and pedicle scarshave notbeen observed.

The

elongate ovalcentral scarsare rather large in the dorsal valve,

and

situatedon eachside of the strong-

median

ridg-e about the middle ofthe valve;

in the ventral valvetheyare

crowded

in with the scars of the middle andoutsidelaterals; the anteriorlateralsare barelydiscernible in one specimenof the dorsal valveas small oval dots on the central ridge a short distance in advanceof the centrals. In the ventral valvethey areclose to the base of the area

and

nearthe outeredge of the shell.

The

middle andoutside laterals in the ventral valve aresituated inthe trapezoidal area, but donotappear to beseparable on the specimens

in thecollection. In the dorsal valvethey are well

shown

in advance of the transmedian scar.

The

latterin the ventral valve is merg^ed withthe anterior lateral.

Of

the vascularmarkingsthe

main

sinuses of the ventral valve are aboutall that areclearly shown, although the positionof the parietal scaris indicated in advance of the center of the shell.

One

of the most strongh^

marked

characters of the dorsal valve is the

median

ridge; itvaries in strengthandoutline in differentshells, butisusually aprominent feature; it extendsto the frontal

margin

in

most

shells,

but in

some

it narrows and is less prominent anteriorly.

A few

specimens

show

a slight depression crossing it just in front of the central scars,

and

one has

two

minute anterior lateral muscle scars directly on the ridge, the parietal scarpassing across just in front of them.

The

thickened shell beneath thevisceralcavitj" of the ventral valve is present in nearly all adult shells; it varies greatlyin size, form, and thickness; in

some

valves it covers the entireareawithin the parietal scar, andin others onlya portion.

The

thickening in the dorsalvalve is along the posterior border ofthe central cavity; this is best

shown

in the cast; the median ridge is also frequently mor(^ or less enlaro-ed.

680 PROCEEDINGS OF THE NATIONAL MUSEUM.

^vol.xxiii.

Formation and

localities.

— Lower

Cambrian. Linie.'?tone cong-lom- erates at Bicand St, Simon, on the St.

Lawrence

River, Provinceof Quebec, Canada. Also in

Lower Cambrian

limestones, l)oth l)edded andcono-lomerate, on the ridge east of Troy.

New

York, and 1 mile south of Schodack Landing, Rensselaer County.

New

York.

BICIA

WHITEAVESI,

newspecies.

This species is associated with

B. gemma

in a bedded limestone at Tro3%

New

York. Itdiffers

from

the latter inthe dorsal valve

by

the absence of the median ridge, the presence of a broad area, and the presence in the interior of both valves of

two

large, circular, scar- like spots, oneon eachside ofthe

median

line andjust in front ofthe area, that recall in appearance and position the posterior adductor scars of Crania.

The

ventral valve isso

much

^like that of

B. gemma

thatit is difficult todecidewhether

some

shellsshould notbe referred to

B. gemma.

There isagradualtransition, in

form

and character of the interiorof the ventral valve,between the extremes represented in

B. gemma

and the extreme

form

of

B.

whiteavesi. If it had notbeen forthe bosses of the dorsal valveassociatedwith ^itI shouldhave hesi- tated to referit toa distinct species.

Formation and

locality.

— ^Lower

^Camlirian.

Bedded

limestone in siliceous shale on ridge in the eastern su1)urbs of Troy,

New

York.

OBOLUS, Additional notes

on.

Ohservatwns.-—T)\'. Mickwitz^ has given, inhisexhaustive

memoir

on Obolus, aver}^ complete historical sketch and full description of the genusand its subgenera so far as

known

to him.

The

material

was

so well preserved, and the study

was

conducted with such care and thoroughness, thatour present

knowledge

ofthe adultshell of Ol)olus isas completeas that of the adultshell of the recentLingula. Inthis note I shall present only such details as are essential to an under- standing of the relations of ₍₁₎ Obolus to Lingula; ₍₂₎ Obokis to Obolella; (3) Obolus toits subgenera.

The

studentisreferredtothe

memoir

of Mickwitz for the literature, history, a geological sketchofthe Caml)rian formations of the eastern Balticregion of Russia, a minutedescriptionof the externaland inter- nal charactersof the shellsof Obolus, an expositionof the relationsof Obolusto Lingula and Obolella, anddetailed observations on Obolus and its subgeneraas

known

to him.

Ohahis a)id Lingula.

—

After studying the species

from American

rocks and aver}^

good

series

from

the typical localities in Russia, I

am

prepared to agree with Mickwitzthat Obolus should ])e referred

^IJberdieBrachiopodeugattimg Obolus Eiehwald:]Mein.Acad.Imp.Sci. St.Peters- bourg,8thser., IV, Xo. 2.

NO.1229.

CAMBRIAN BRACIIIOPODA—WALCOTT. ₆₈₁

to the LingulicUv. andthat there is no

good

reason forcstablishino-the famil}' 01)olida\

Their points of simihirity as described

by

Micl\witz are:

1.

The

chemicalconstitutionand microscopic structure arc the same.

2.

The

position of the

umbonal

muscle is the

same

in the dorsal valve.

3.

The

arrangement of the vessels of the circulator}' system isthe

same

in the

two

genera. Mickwitz sa3's of this:^

Issuing betweenthesamemusclesearsfromthe splanchnoccele, two mainvessels extendineachvalveintotheforepartof themantleloljes and brani'h inward and outwardintonumeroussecondaryvessels. Theonlydifference in the arrangement of thevessels consists in this, that in Lingula the mainvessels of the twovalves emptyintothe peripheralcanal, while in Obolu.s thistakes place only in the large valve. Inthe small valve the mainves.sels, shortly before reaching the perij^heral canals, l)end intotheinterior of tlie valves and end atthescars of the anterior lat- eralmuscles.

i.

The

general arrangement of the muscle scars is essentially the same, the points of difference being of agenericcharacter.^

Their points ofdifference, according to Mickwitz. are:

1. In the area of the valves.

'2. In Lingulathe pedicle muscleisattached backof the scar ofthe

umbonal

muscle of theventral valve, while in Obolus it is situated between thedivided scar of the

umbonal

muscle of the ventral valve.

3. Quoting

from

]\Iickwitz:

Besidesthesomewhat unlike arrangement of somescars,towhichwe shall pre- sently return, thebipartition of certainmuscles constitutesthe most characteristic difference in theinternalorganization of the two genera. Theumbcjnal muscleof Obolus,whichisdividedon the side of the large valve, while conversely the two transmedialmuscles of Lingula, oneof which ^is dividedthroughout itslength, are representedinObolusbya pairof undividedmuscles.

Thepositionoftheumbonal muscle is the same in the twogenera; atmostit is

somewhatcrowdedawayfromthe baseofthe areainLingula,becauseofthejiedicle muscle.

On

the contrary, thetransmedial muscles, besidestheir bipartition, pre.sent otherdifferences. In Obolus thescars of that partofmuscles onthelargevalve are combniedwiththoseofthe anteriorlateralmuscles,whileinthecorrespondingshell ofLingula, thoughlyingina similar position, theyare separated fromthe anterior lateralmuscles. Withthe small valves thecaseisreversed. 01)olusshowsthescars ofthe pair of muscles inquestion isolated, while in Lingula they are united with thoseofthemiddleandoutsidelateralmuscles.

Thescars ofthetwolast-named musclesonthesmall valveofOljolusarecombined

in a manner analogous to those of Lingula, so that the whole difference in the arrangementof thescarsinquestion (aside from thebipartition of onetransmedial muscleinLingula) consistsinthereversal of theircombination. InObolus, onthe large valve,thescars(andjareunited, inLingula theyareseparated;inLingula,on thesmallvalve, iand/;, /, areuniteil, whileinObolus theyare separated.

Thescars ofthe anteriorlateral nuiscles of the small valvehaveaclosely similar position inthetwogenera,except that in Obolus theyare moved fartherforward, andare separatedbythemedianridge,whileinLingulatheyarenearertothe center ofthe valveandare'united.

^UL'erdie BrachiojiodengattungObolus Eichwald, \i. 121.

682 PROCEEDIXGS OF THE XATIOXAL MUSEUM.

^vol.xxiii.

Theotherscars ofthelateral muscleson the large valveof Obolusalsoarequite analogousin theirpositiontothe correspondingscars inLingula. True,intheir case, alsosmalldisplacementsandchangesofformoccur,butyetI

am

unabletoattach to theseanyspecialvalue. The two generashowthe scars ofthe outsidelateralmus- clescombinedwiththoseof thecentralmuscles,butwe haveseen thatinsomespe- cies of Eichwald's genus (0. trkingularis, 0.pamhri,and some species of the sub- genusSehmidtia)^,the first-named scarsseparate from those of thecentralmuscles andchangetheirsubtriangular form,drawnoutbackward,intoaroundedform,more

likethatinLingula. Thescars of themiddlelateral musclesof thelarge valve,on the contrary, are onlyin Eichwald's genuscomljinedwiththoseof thecentral nms-

cles,whileinLingulatheyare separated. Itisprobable,however,thatsomespecies oftheabove-namedsubgenussharethis peculiaritywithLingula.

Finally, thescars of thecentral musclesof thetwogeneradiffermerelybytheir somewhatdifferentforminthelarge valve,and bytheirsomewhatdifferent position withrelation tothe axisof symmetry on the smallvalve. Itwaspointedout, how-

ever,inspeakingofthecentralmusclesofObolus, that thebackward-protractedpoints of thesu1)trapezoidal scarsinthe largevalveof thetypical species (aswellasthose ofthe outside lateral muscles) are lackinginthespecies of thesubgenusSehmidtia, sothateven in regard to form there is an agreement with Lingula. In the small valveofObolustheellipticscars ofthecentral musclesareparallel tothemajoraxis ofthe valve orsomewhatconvergingbehind, whileinLingula theyarestronglycon- vergentanteriorly.

Tothealteredpositionofthemusclescars inOboluscorresponds themodifiedform oftheparietal band. The latterin bothvalves of Lingulais rhombic, butin the smaller valveitisdrawnfartherforward thaninthelarger. InObolustheparietal

bandonthe small valveextendsstillfarthertowardthefrontaledge thaninLingula, and initsposteriorpartismore markedlybent inward from both^sides,producinga characteristicunequallythree-lobedfigure. Theparietalband ofthe largevalveof Obolus,onthe contrary, issubelliptieinform, andratherapproachesthatofLingula.

More important than this difference in form of the splanchnocade is the dif- ference in theformof themantlelobes, whichismanifest fromthe position of the posterior part of the parietal band. In Lingula the parietalbandis moved away from the base ofthe area, and thus constitutes a narrow space betweenthe two pleurocoeles,whichspace ^is occupied by the mantle lobes that extendaround the entire beak part of thevalves. These mantle lobes of the beak are in the small valvealsocoveredwith mantlebristles, while the borderofthemantleof the large valve, inthe splanchnoccele partofthe area (deltidiumKing) is free from bristles.

InObolus, onthe contrary, the posterior partoftheparietalbandisclose tothebase ofthe splanchnoccele partof thearea, whose lamellte, aswe haveseen,arel)ent up

at rightanglestothe planeofthevalve,andtherefore could nothave beendeposited by mantlelobes resting against the valves. Hence the mantle lobes of Obolus extended only as far as the pleurocoeles, and were lacking, as wellas the mantle

bristles, inthe splanchnoccele part of the area of bothvalves. Atthatpoint there wasonlythemuscularwall of thebodyconnecting thetwovalves,fromwhichthe pedicleemerged.^

Oholm and

Olxjldla.

—

Authors have

compared

Obolella with

Obo-

lus, and

Mickwitz

thought that they might possibly be congeneric.^

The narrow

pedicle slit in the area of the ventral valve of Obolella openinginto a cylindro-conical

chamber

is so unlikethepedicle fur- row^ of Obohis that a distinct generic reference is necessitated

by

its

^tjber dieBrachiopodengattung Obolus Eichwald,pp.118-121. -Idem,p. 129.

NO.1229.

CAMBRIAN BRACUIOrODA—WALCOTT. 685

discovery, despite the g-reat similarity of the

two

genera in other respects. Except for the pedicle slit and chamber, the species of Obolella could not well be taken

from

Obolus.

OBOLUS AND

ITS SUBGENERA.

LinguIeUa Salter. I have been at times almost doubtful of the advisability" of characterizing Lingulellaeven as asubgenusofObolus.

This distinction is

now

based on the

more

elongate

form

of

most

of the species ofLingulella and the greater thickness of theshell of the typ-

ical formsof Obolus.

Type.

—

Oholus {LlvgultUa) davisil.

Lingulejns Hall is anelongate, acuminate

form

of Lingulella, thus departing

most

widely in

form from

Obolus.

Type.

—

_Oholus {Lingulejyis) acununatus.

Linqidoholus

Matthew

is a Lingulella-like form, with a very thick shell.

'

Type.

—

Oholus {Lingulohohis) affinis.

' Schmidtia VolborthisaLingulella-likeshellwithoutradialstriation.

All the species are small,and as the concentric stride are veryline the shellsurface is nearly smooth.

Type.

—

_Oholus{Schrnldtia) celatiis.

WesfoniaWalcottisaLingulella-like

form

distinguished

by

peculiar, transverse,semiimbricating, ''ripple-embossed" lines that cross both the concentricand radiating strife.

Type.

—

Oholus {We-'<toma) aurora.

Thymnotos

Mickwitz.

An

Obolus with strong, uniformly curved- concentric strife, with lamellae of

growth

fringed along theiranterior (external) edges.

Tyjje.

—

Oholus {Thyseuiotus) slluricusEichwald.

Acritis Volborth. Concentriclines elevated, irregular, undulating.

Valvesstrongly arched, massive. Visceral area(splanchnocoele) small andshort; pedicle furrowconicaland deeplyimpressed in area.

TyjM:.

—

Oholus {Acrit(s) antlqidsslmusEichwald.

Leptemholon Mickwitz. This subgenus is ratherdifficult to charac- terize. Mickwitzsays of it:

The subgenus Leptenibolon is based ou a species of Obolus which externally resemblesLingula veryclosely,andin factwasbyearlierauthors^regardedassuch.

Thespecimensofthe internalsurfaces ofthevalves,however,showed,togetherwith -ninesuggestionsof the last-mentionedgenus(Lingula), unmistakablemarksof the genus Obolus, sothat thespecies,which could not beassigned toanyof the other groups, hadtobe rankedinaspecialsubgenusofEichwald'sgenus."^-

Typif.

—

(^hejlus {Lepteudxjlori) Ungulo'forrnis Mickwitz.

^Schmidt,Fr.,Ke\asiondersilurischenostbaltischen Trilobiten, Pt. I, p. 17.

^tjber dieBrachiopodengattung Obolus Eichwald, p. 199.