CAMBRIAN BRACHIOrODA: GENERA IPHIDEA AND

CAMBRIAN BRACHIOrODA: GENERA IPHIDEA AND

YORKIA, WITH DESCRIPTIONS OF NEW SPECIES OF EACH, AND OF THE GENUS ^ACROTHELE.

By Charles

^D.

Walcott,

HonoraryCurator, DepartmentofInvertebratePalaontology.

This

is

the

tirst of a proposed series ofpreliminary papers outhe

Cambrian

iBracliiopoda, tobe^publishedin advanceof a

memoir

on the subject.

Owing

to administrativeduties,only a small part ofeachyear canbe devoted

by me

to pala'ontologic studies. In the presentpaper thegeneraIphidea

and YorVm

are discussed. Succeedingpaperswill treatof otherwell-known genera.

IPHIDEA,

Billings.

Iphidea, Billings,1872, Cau.Nat.,newser.,VI,p. 477,^{tig. 13.}

Mtcromitra,Meek,1873,SixthAnn.Kept. U.S.Geol. Surv.Terr., for 1872,p.^47!1.

Iphidea,Billings, 1874, Pal. Foss.,II,Pt. 1,p. 76.

Iphidea, Linnarsson, 1876, Bihang Till K. Svenska Vet. Akad., Haudliugar, No.12,p.26. Brachiopodaof theParadoxides BedsofSweden.

Iphidea, Walcott,1886, Bull. U.S. Geol. Surv.,No.30,p. 100.

Paterina, Beechek,1891, Am.Jour. Sci.,XLI,p. 345.

Iphidea,HallandClarke, 1892, Pal.N.Y., VIII, Pt. 1,p.97.

Iphidea,HallaudClarke,1892,Eleventh Ann. Kept. Stat.-Geol. N.¥.,p.249.

Paterina,HallandClarke,1892,Eleventh Ann.Kept. StateGeof.N.Y., p.217.

The

description of the genus Iphidea

and

thatof the type species were combined.

At

the time of

my

^{studyof Kntorgina}

^and

^IphideaI

did not agree withMr. Billings in his reference of

Oholm

labradoricus toKutorgina,^ overlooking the^factthathe

had

referred 0.lahradoricus toIphidea.'^ Since that time ^I havecollected

more

materialrepresent- ingthisgroupof shells,

aud

from itsstudy have

come

tothe conclusion that Mr. ^Billings

was

correct in referring 0. lahradoricus to Iphidea.

The

ventral valve of0. labradoricushas anarrowfalseareaofthe

same

type asIphidea bella,

and

tlie characteristic pseudodeltidiumisclearly

shown

in a section,

and

it is

known

to occur inJ. sculpt His.Meek, I.

ornatella, Linnarsson,

and

I. pannula,White.

The

extreme develop-

ment

of the false area

and

pseudodeltidiumisfoundin an undescribed

1Bull.U.S.Geol. Surv.,No.30,1886, p. 100.

"-Pal. Foss.,II,Pt.1,p. 76.

Proceedings U.S. National Museum,Vol.XIX—No.1120.

708

^CA

MBEIAN BHACHIOPODA— walcott.

speciesof Jphidea{I. superha) from the Middle

Cambrian

Tontosand- stone(»f the (irand

Canyon

of the Colorado. In this form the ventral valve isbioadlyconical,

and

the larjie j)scudodeltidium projects back-

ward

atanangle equaltothat of theslopefromtheai)ex tothefront. In

I.bdlatliofalseareaslo])es

more

abruptly

downward,

andin f.onudelhi

it isnearly vertical, the pseudodeltidium being

much

shorter

and

pro- jecting but a short distance

beyond

the area.

The

slopeof the area of/. ornaieUa is essentially the

same

as that of /. lahradoriat var.

su-antonensifi, which ^is the type of Mr. Ueecher's genus Futerina. In

some

specimensof thelatterspeciesthebeakprojects sothatthe slope ofthe areacarried^it forwardtoa considerable distanceunderthe beak.

This is also trueof I.pannula.

The

presence of

an

apical foramen in I. bella

and

/. ornatelln would separate thegenus from Paterina, but,from acareful study of allthe evidence attainable,I

am

led to question the presenceof atrue apical foramenin either species. Unlessthere areother characters than^tliose

shown by

thefalse area

and

i)seudodeltidium

and

the angle atwhich theyslope, itwill beimi^racticable togenerically separate I. bella

and

I. J((br<tf1oricus

and

the other speciesmentioned.

Inhis original description, Mr. Billings says:

In the specinieu above figured there is au apertureiuthe beak, but in another thereisno appearance whateverof aperforation.'

Professor

Whiteaves

writes me, under date of July 23, 189G, that there are no si)ecimens or electrotypes of the types of I. bella in the collections of the Geological Survey of Canada, nor of the closely allied species ofthe

same

genus from Topsail Head, mentioned

by

Mr. Billings.

Under

the circumstances, nothing can be done but to decidefrom Mr. Billings's description

and

figure the charactersof the genus

and

species,

and

refer to thespecies theform that can bestbe identifiedwith the description

and

figure as the specific type of the genus. This appears to be the species from the

York

limestone of Pennsylvania.

In a fine series of Iphidea bella from tlie

Lower

Cambrian, south of Emigsville,

York

County,Pennsjdvania, thecharacteristicsoftliegenus

and

speciesarestrikingly wellshown. Innoneofthespecimensisthere in the ventral valvean indication of an apical pedicleopening.

The

dorsalvalve isslightlyelevated,

and

in the half dozen well-preserved specimens no trace has been observed of

any

false area or pseudo- deltidium; butin 7.pajmulathefalsearea iseven

more

clearlydefined than in the ventral valve,

and

the pseudodeltidium is ])resent as a depressed concave covering of

more

than one half of the triangular space inside the narrow area on ea(;h side.

The

area on the dorsal valvehasalsobeen observedin I, oruatella

and

/. labradorka.

Doctor liinnarsson, indescribing/.ornatcUa, speaksof the presence of a minute foramen; but, afterthestudy of several finely preserved

'Pal. Foss., II,Pt. _1,p.76.

NO.1120.

FBOCEEDIXnS OF THE NATIONAL MUSEUM. ₇₀₉

ventral valvesfrom theParadoxidesbedsof

Andrarum,

Sweden,I

am

led to believethat

what

he considered to be an apical foramenis a depressionin the apex of theshell infrontof theincurved beak,Avhich representsa foramen which

was

piesent in oneof tlieembryonic(nepi- onic) statues,

and was

subsequently lost. This would involve the crowding- out, asit were, of thepedicle posteriorly, the only evidence of itsi)resence in the adultbeing the narrow, slightlydepressed slitat theapexof the valve in

some

specimens.

The

pedicle in the adult shell is i)rotruded between the

two

valves

and

separated from the embryonici)edicle opening

by

the growth of a pseudodeltidium.

The

examination of the

somewhat

closely allied form, /.

panmda^

shows thei»resence in

some

specimensof theapicaldepression

and

its

absence in others. In an undescribed species, I. siqyerba, still

more

closely approaching the type /. bella in external appearance, thereis

no trace of an apical slit or foramen. lu another species associated with /. superba {I. crcnistria) theapex is rounded, whilein a

somewhat

similar but distinct form [1.penki), froni the GallatinEiver valleyof Montana, the apical slit is as clearly

shown

as inI. ornatella, butnot

any

apical foramen.

Messrs. Hall and Clarke illustrate aspecimen of J. bellashowing an apical foramen, but in the description of the figure the statement is

made

thattheforamen is not altogetherdistinct inthe specimen.'

The

systematicposition of the genus Iphulea appears to be in the Js^eotremata of Beecher,^ possibly with characters that nearly place

It in the Protremata. If the pedicle

was

apical in its early stages

and

inclosed

by

shell growth,

and

subsequently

was crowded back

of a pseudodeltidium, it passed through the Xeotrematic stage to the Protrematic.

The

presence of an obscure listrium in front of the ai)ex of /. bella, I. ornatella,

and some

specimens of I. pealei, tends to support thisview.

We

^alsohave toconsiderthe area ofthe dorsal valve as

shown

in I.pannula. In this species there is a ratiier deep, convex pseudodeltidium in the ventral valve,

and

a clearl^^ defined, depressed pseudodeltidium on the dorsal valve between the narrow

false areas. Thereis alsopresent a narrow

median

groove extending from beneath the apex of the valve to the posterior margin of the pseudodeltidium. It is similar in appearance to the pedicle groove of the ventral valve of Obolns

and

Rhinobohis. This suggests thatit

may

be the pedicle valve; but thepresence of the listrium or

embryo

pedicle scar ontheconical valveis opposed to theinterpretation.

It

may

be urged that Iphideais a trueAtreftiatic genus, the pedicle never having been inclosed and thesliton the ventral valvebeing only a depression without special significance. This

may

be so, but the impression it conveysto

me

^is that the slit indicates a pedicle open- ingnearthe ai)ex of the ventral valve, atan earlystagein its growth,

'Pal.N. Y.,VIII, Pt.1,(lescrii)tionofpi. iv,fig. 8.

2Auier.Jour.Sci.,XLI,1891,pp.354,355.

710

CA

MBRIA X ^BRA CHIOPODA— WALCOTT.

vol. xix.

which

was

subsequently closed, the pedicle then protruding between thevalves,

Tlu' only interior of any specimen of the genus thusfar discovered thatshows atraceof muscularscars orvascular markings is theinte- riorof tlie dorsal valve of I. j)a)i)iuh(, from near

Rome,

Oeorgia. All that is discernible in this is a slight depression in the cast of the interior,about one-third the distance from the beak to thefront.

A

rather strong vascular trunk arches forward on each sideof it. nearly tothe center^of the valve.

iStrafii/raphic<li,sfrihntio)i.

— The

genus ranges from the lowest

known Lower Cambrian

horizon totheupper portion oftheMiddle Cambrian.

The

^{species thusfar}referred tothegenus are as follows:

Lower Cambrian

:

Iphidca hcHa,Billiujj:s.

labradoriea, killings.

var. swiintonensis, Walcott.

j)n)inHla,White.

jyrospecfensis, Walcott.

Middle Cambrian:

Iphtdeacnnistria,news]»e(ies.

alahamaerms,newsi»ecie8.

lo(j(nii,lu'wspecies.

orvaieJla, Linnarsson.

pamntla,White.

2)eah'i,newspecies.

pusilla,Linnarsson.

sculptilis,Meek.

stissingensis,

D

wight.

siiperba,newspecies.

Ornamentation ofthesurface.

— One

of the mostnoticeablecharacters

is the surface ornamentation. In thetype/. bellait isformed of sim- pleconcentric stria'

and

linesof growth. This

may

becalled type

A

and toit

may

bereferred

:

Iphideabella LowerCambrian.

labradoriea LowerCambrian.

var. swatitonensls LowerCambrian.

2)rospecttnxis LowerCambrian;

ahibamaensiii Middle Cambrian.

logani Middle Cambrian.

pnsiUa MiddleCambrian.

siiperba Mid<lleCambrian.

stisKintjenifis Middle Cambrian.

i-renistria Middle Cambrian.

peaJci Middle Cambrian.

The

second type^{(B) is} represented

by

I. ftculjytiUs,in whichthe striae

are

more

crenulated than in J. crenistria,but not sulliciently so togive a diamond-shapedinterspace.

Type C

is abeautiful surface, formed

by

theunion of the crenulated

striieso as to

make

a line network of raised, obliquelyarranged lines

NO.1120.

rROCEEDIXGS OF THE NATIONAL MUSEVM. 711

that divide the surface into minute pits that give the impression of iiuely

woven

cloth. T. ornateUa

and

I. pannula represent this type.

Among

^{other generait}

may

be found in Treniatis;

and

the second type ofsurface, as

shown by

I.sculptiUs,is frequently seenon Llngulella.

IPHIDEA SUPERBA,

new species.

(PlateLIX,tiys.1,\a-e.)

IpMdea cf.? ornateUa, 1892, Hall and Clarke, Pal. N. Y..VIII,Pt. 1,^jil. iv, figs. 6, 7.

Ventral (pedicle)valvesubcorneal,witha minute

beak

incurving over the pseudodeltidium. Cardiiuilslope slightly flattened, soastomerely indicateanimperfectlydeiined,rathernarrowarea. In

some

specimens the curvature of theshell is practically continuous to the base of the pseudodeltidium. Pseudodeltidium broad, convex,withitslower mar- gin broadly arched,so as to leave a considerable space between it

and

thelineof the general plane of the shell.

Dorsal(brachial)valveslightlyconvex; mostelevated alittleinfront ofthe small beak which projects slightlyover the broad open (?) del- thyrium.

No

traces of a false area or a pseudodeltidium have been observed.

Surface with rather strong concentric striie,

and

a few

somewhat

obscurelinesofgrowth.

On

the ventralvalve thestriicextend around to

and

cross the pseudodeltidium. Shell substance corneous.

Thisis oneofthelarger species ofthegenus,beingsurpassedin size only

by

I. labradorica. It is clearly distinguishable from I. bella

by

its larger size,

more

depressed ventral valve,

and

the form of the pseudodeltidium.

The

dorsal valves of the

two

species are quitesimi- lar. It differs fromI. pealei in its broad pseudodeltidium, false area,

and

surfacemarkings.

One

specimen has a length of

mm. and

a ^littlegreater width.

The

areaisvertical, tbepseudodeltidium being broken away.

Formation andlocality.

—

Middle Cambrian, TontoTerrane,

Ohuar and and Nunkoweap

valleys,

Grand Canyon

of the Colorado. (No. 20429, U.S>N.M,)

IPHIDEA LOGANI,

newspecies.

(Plate LIX, figs.2, '2a, 2l>.)

Ventral (pedicle) valveconical, transversein outline at base, almost semicircular.

Beak

minute, incurving over the pseudodeltidium.

Cardinal slo])es rounded

and

flattened so as to form a fairly well defined false area that is broken

by

a verywide triangular space.

Pseudodeltidium arched upward, forming a narrow, sloping shelf beneath the beak, the angle of slope from the

summit

of the shell over the beak

and

i)seudodeltidium being nearly the

same

asthat of theslopefrom the

summit

to thefront.

Surface

marked by

veryfine concentricstriie and

somewhat

coarser linesof growth.

Under

a high ]>()wer slight traces of radiating striai

712 CAMBRIA X BRA CHIOVODA— WA LCO

TT.

may

be observed.

The

concentric stiite pass around over the false area

and

crossthe pseudodeltidium. ^Shell substance corneous.

Thisspecimen

was

receivedfrom ProfessorJ. F. AVhiteaves asoneof the typesof/. belhi. It differs,however,somateriallyfrom thedescrip- tionof that^species

and

thefigure illustrating-itthat I found it neces- sarj-to give it a distinct specific designation, and I take pleasure in

naming

^{it after Sir William K. Logan.}

The

specimen ^{bears the label "Trois Pistoles,} 18GS, T. C. Weston.'' It

was

^{collected from a bowlderin tlie} conglomerat*' at that locality.

Itis probablyof^Middle

Cambrian

age, but thiscan not be statedwith certainty, as thereare noassociated fossils. Mr,Bdlings speaksofthe occurrenceoffragments^oftrilobites in thebowldercontainingthistype of/. Ix'Ua.

He

does notmention the j^eneraor species.

The

species a|)proachesmost nearly /. crrnistyin in its short pseudo deltidium

and

finelystriated surface. It differs, however, in thechar- acter of the surfacestria', the form ^of the false area, and the pseudo- deltidium.

Formation and locality.

—

Conglomerates at Trois Pistoles onthe St.

Lawrence, Provinceof Quebec.

The

conglomerates ofthis formation, according to Sir William E. Logan, form nine separate layers, from^- to1() feet thick,l)edded in gray, calcareous sandstone.

The

geclogic ageof the deposit containing the matrixis supposedto be ITpper

Cam-

brianor

Lower

Ordovician.

The

age of thebowlders canbedetermined only

by

the fossilsfound in each.

IPHIDEA PEALEI,

new species.

(PlateLIX,figs.8,3a-3c.)

Ventral (pedicle) valve subconical, beak slightlyincurving over the pseudodeltidium. Cardinal slope fiattened toforma narrowfalsearea, which is clearly defined from the curvature of the shell

by

slightly elevated thread-like ridges. Pseudodeltidium comparatively narrow, strongly convex, and arched below.

The

^{stri.i^} of growth cross the false area andarch over the delthyrium.

Dorsal (brachial)valve moderatelyconvex,

and

without

any

special characteristics to distinguish it from the

same

valve in /. bella, I.

f^-'q)erh<(,

and

J. lahradorica.

Surface

marked

byfine concentric striae

and

lines ofgrowth thatare usuallyplain, but iu

some

examplesare slightly crenulated. In such instances fine radiatinglinesor stria' are also shown. Shellsubstance corneous.

Intlie mostperfectlypreserved specimens there is a slight slit or depressionnear the apexof the ventral valve,but thereisno trace of aperforation or apical oi>eiiing.

This species apju-oaches7. ficidptilis iu

some

examples of the ventral valve. It ditters mainly in thenarrow pseudodeltidium and the char acter of thesurface markings. Itmiglitbeconsidered asafi)niiint^r- me<liatebetween /. hella and /..srHlptiHa.

Ko.liiiO.

PROCEEDINGS OF THE NATIONAL MUSEUM. ₇₁₃

Specitic

name

in honorof Doctor A.C. Peale,

who

collectedthe type specimen.

Formation andlocality.

—

MiddleCambrian, FlatheadTerrane. Xortli of EastGallatin Kiver,north of Hillsdale,^Fonlana. Also,on the east side of Gallatin Kiver above Gallatin City. (J^o. 2G430, 17.S.X.M.)

IPHIDEA CRENISTRIA,

new species.

(PlateLIX,ligs.4,4a,4&.)

Pediclevalve subconical,beaknearly apical,curving slightlyover to the psendodeltidiuin. False area very narrow, separated from the curvature of the shell

by

being turned

somewhat

abruptlybackward.

Pseudodeltidiumcomparatively broad,butdecidedly short as

compared

with thntofI. hellaor 7.fiupcrha. It is

more

ofthetyi)eof/.lahrulor- im. Itis stronglyarched, leaving a broad, high space between it

and

theplane of the shell.

Dorsal(brachial) valve

unknown.

Surfaceofventral (pedicle) valve

marked by

^{very fine, slightlycrenulated stria*} that areso

crowded

on thefalse area that theyarenearly lost,

and

only oneor

two

varices of growth

and

afew strine are

shown

on thepseudodeltidium.

No

traces of an embryonic; foramen are seen, save the slight slit at the apexof theshell.

This species is clearly distinguishable from other described forms of thegenus

by

itshighly arched pseudodeltidium

and

crenulatedsurface striic.

Formation and locality.

—

^{Middle Cambrian, TontoTerrane. In thin}

intercalated limestone layers nearhead of

Nuukoweap

Valley,

Grand Canyon

of the Colorado. (No. 20431, U.iS.N.M.)

IPHIDEA ALABAMAENSIS,

new species.

(PlateLIX, fif^s.5, 5rt.)

In following the

Lower Cambrian

rockssouthward from Vermont,the

firsttypeofIphidea

met

with is/.stissingensis,whichoccursintheMid- dle

Cambrian

of Dutchess County,

New

York. This is fairly welldis- tinguished by itssurfacecharactersfrom I. lahradorica

and

its variety sicantonensis,butatthe nextlocality tothesouth, ineastern Tennessee, four miles north of Eogersville, in the Ivogersvilleshale of the Middle Cambrian,w;)S found a form that is practically identicalwith thenorth- ern species or its varietj^,as farasit is possible tocompare specimens preserved in limestonewith those preserved inshale.

The same

form also occurs intheMiddle

Cambrian

shales of the

Cowan

Creek section, Cherokee County, Alabama. Thereis,however, adifferencein thesur- face stria' that distinguishes^itfrom 7.lahradorica

and

itsvariety

and

7.

stissi)i(jen.sis. It is the tendency to crenulation of the stria' in nearly

all the specimens that have been examined. This in extreme cases goessofar as toapproach the surface, so characteristic of 7.pannula.

714 CAMBRIAN BRACHIOPODA— ^WALCOTT.

The

form can^notwellbeidentifiedwith theclosely related/.labradorica or^itsvarietySH-antonensis, or/. stissiiigeufiis,onaccountofthesepecul- iarsurface characters,

and

the

name

I. alabamae)isi.sis])roposed forit.

In general formof thevalves thisspeciesis the

same

as /.labradorica andI.stis,si)u/(')isi.s.

The

^sj)eciti(;<litTcrencefrom them,asfaras known,

isin the surfacecharacter.

The

convexity of the valves is

unknown,

owin<;-to the con)pression ^of the sliells in the shale,

and we

have no information of the area orthei)seudodeltl(lium. It

may

be that with the obtaining ^{of better material, especially} from the limestone, this specieswill be referred to as a variety of I. stissingensis. Shell sub- stance corneous.

Formation and^localiti/.

—

Middle Cambrian, Coosa Valleyshale.

Cowan

Creek section, Cherokee County,

Alabama;

^also in Rogersville shale, 4 milesnortheast of Rogeriiville,Tennessee, back of BigCreek, south- east of Harlans Knob. (No. 2G432, U.S.N.M.)

YORKIA,

newgenus.

Shell inarticulate, subcircular to suborbicular in outline.

Apex

of ventral (pedicle) valve perforate, marginal, with a falsearea

and

a pseudodeltidium.

The

cast of the interior of the valve

shows

a fora-

men

which penetrated obli(]uely

upward and backward

through the thick

umbonal

portion of the shell.

Two

narrow furrows converge fromthe side of the foraminal openingtowardthe longitudinal mesial depression

and

then divergetoward the anterolateral portions of the shell.

The

dorsal (brachial) valve has a well-defined area

and

an obscure pseudodeltidium.

The

interiorofthisvalvehasapairofbroad,diverg- ing, shear-shaped furrows passing directlyforward from the beak for ashort distance

and

then div^erging tothe outer margin, but not suf- ficiently to affecttheoutward curveof the inner margin.

Shellsubstanceprobablycalcareous. External surface

marked

with

more

orlessi^rominent concentric stria^

and

linesof growth.

Ti/pe.

—

¹orli-ia icanncri.

The

area

and

])seudodeltidium of the ventral valve resemble the

same

parts in 'fremafobolxs insignis, Matthew,' but the foramen is quitedifferent,and generally the interiorofthedorsalvalvealsoserves to distinguish the forms.

To

J)iscinop.sis, Matthew,- there isa resem- blance inthemarkingsof theinteriorofthe dorsalvalve. Discinopsis, however, is founded upon a small, apparently corneous shell, which so far as known, has no area or pseudodeltidium, and it is closely related to Acrothele. Yorkia differs from Acrothelc in its pronounced area,substanceof shell,

and

])lace of origin ofvascular trunks. I do not

know

of anyother genus of the tiiphonotretida' with which it can be compared.

'Can. Rec. oiSci.,V,18i)8,p.277.

n^al.N.Y., VIII, Pt. 1, 181t2,p. 105.

NO.1120.

PROCEEDINGS OF TEE NATIONAL MUSEUM. ₇₁₅ YORKIA WANNERI,

new species.

(PlateLX, figs. 1,\a-\e.)

Shell subcircular to suborbicular in outline, moderatelyconvex, with the apices of the valves marginal. Ventral (pedicle) valve highest at the beak, which is truncated

by

a circularforaminal opening; car- dinal slope angular

and

slightly incurved, so as to form a narrow

false area on each side of the slightly convex, rather broad pseudo- deltidium.

Xnmerous

casts

show

the pseudodeltidium, falsearea,

and

alargefillingor cast oftheforamen which extendedobliquely

backward

through the thickened

nmbonal

portion of the shellto the apex.

On

a castoftheinteriorofthe valve there are two elongated muscular or vascular (probably thelatter)impressions that extend from the antero- lateralbase of the foraminal openinginwardtonearly the

median

line,

and

then diagonallyoutward towardthe anterior lateralmargin of the shell. Thereis alsoaslightmedian longitudinal ridge that corresponds to ade])ressionin the interiorofthe shell. (Plate

LX,

figs. l/>, Ic) In othercasts strije or linesonly are

shown

radiating

outward

from the base ofthe foramen. Fine transverse strife crossthe narrowarea

and

then incurve and cross the pseudodeltidium.

The

dorsal (brachial) valve has a well defined area, withan obscure pseudodeltidium parting it midway.

The

cast of the interior of the valveshows two broad,shearshaped diverging ridges thatextend from near the apex to the center of the shell.

Xumerous

vascular markings extend outward from the ridges. These ridges

may

indicatethe mus- cular sears or merely the

main

trunks of the vascular depressions.

The

surfaceoftheareais

marked

l)yfinetransversestri;ethat abruptly' incurvetoward thefront of tliearea, so as to follow along itsanterior margin tothe pseudodeltidium.

The

surfacesofbothvalves, as

shown

inthecasts, aresmooth, except where

marked by

concentriclinesof growth.

Shellsubstance

unknown,

but probably calcareous. It is dissolved

away

inall thespecimensin thecollection, only the impression of the shellremaining in thedecomi)()sed arenaceous limestone.

This species occurs in abundance, associated with BilUngseUa fes tinata, Hyolithes americanus, tSalterella coiiica,

new

species,

and

frag-

mentsof Olenellus.

Formation and loadity.

— Lower

Cambrian,

York

Terrane, on left

bank

of Codorus Creek, one-eighth of a mile below Meyer'sJVlill, near Emigsville, 4milesnorthofYork,Pennsylvania. (No. 2G433,U.S.X.M.)

YORKIA? WASHINGTONENSIS,

new species.

(PlateLX,^fig.3.)

Ventral (pedicle) valve longitudinally ovate, depressed, convex.

Area and

pseudodeltidium invisible,but, from thecharacter of thefor-

amen and

its resemblanceto the foramenof l'. wanneri,it isprobable

716 CAMBIUA N an

A

(HIorODA—WALCOTT.

that the area

was somewhat

^{simihir to tlie:ireaof thatspecies.}

The

cast of the ^inti'rior of the ventral valve shows a rather long, large foramen, in advance of which two ridges (vascular trunks) diverge sonunvhat,as in the ventral valve^{of 1'.} inonieri. Thereisalso jjresent a sliort longitudinal dei)ression in the cast, which indicates a corre- sponding mesial ridge justin advance of theforamen.

The

surfoce of the interior of the shell is

marked by

fine concentric lines and very fiueinterior ridges. Shell substance apparently corneous.

This species is founded upon

two

semic^asts of the ventral valve, preserved in comi>aet gray limestone.

The

shell appears to be ^verj' thin over the outer iiortionsand tliiekover the

umboual

region.

The

generic reference is

somewhat

doubtful,

owing

to the close generic ^relations of Yorlia, AcrotheJe, and Discinopsin.

The

foramen and form of the vas<'nlar trunks suggest Yorlia, while the shell substance

and

surface charactersarc

more

those ofAeroihclc.

Formation and ^loeaJiti/.

— ^Lower

Cambrian, one-fourth mile east of Salem,

Washington

County,

New

^York. (Xo. 2G434, T\S.N.IV[.)

ACROTHELE DECIPIENS,

new species.

(PlatoLX,fij.-. 2.)

General formofthe ventral (pedicle)valve nearlycircular,thelength

and

breadth beingnearly thesame; moderatelyconvex, mostelevated at the apex, which is truncated by a rather largeforaminal opening.

Cardinal slopesrounded, forming anobscurefalseareaoneach sideof the flattened pseudodeltidium, which appearsto haveaslight groove

down

itscenter. Surface

marked by

^fineconcentric stria'

and

linesof growth, which pass around back over the area

and

pseudodeltidium.

Shell substance corneous,or it

may

bej^hosphatic.

The

shellhas the

same

appearanceas AcrotheJe

and

Linnarssonia.

Only

one specimen of this shell

was

found associated with Linnars- sonia and fragments of OleneUns, in a fine gray limestone interbedded inthe

Lower Cambrian

shale. Itresembles quitestrongly the ventral valveofI)iscino2)sisfjidielnii,IMatthew,illustrated

by

Hall

and

Clarke.' It difiers,however, inthepresenceofanobscure pseudodeltidium,

and

forthe present I prefer to j)laceit with Aerotlieic until more is

known

of thegenus J)iscmo2)sis.

Formation and h>C((Jity.

— Lower

Cambrian,

York

Terrane^, !>!, miles north of Stoner's Stati(m,

York and

Wriglitsville llailroad,

York

County, Pennsylvania. (No. 26435, T.S.N.M.)

ACROTHELE BELLULA,

new species.

HMateLX, figs.4,4a-4e.)

General form of valves subcircular, moderately convex. Ventral (pedicle) valve highest at the apex

and

perforated

by

a circularfora-

men, in frontof which there are two small, sliort, sharp spines.

The

I]'al. X.v., VIII. I't. I, 1,S1L\ 1.1. Ill, W'

NO.H20.

rROCEEDiyaS of the XATIOyAL MUSEUM. ₇₁₇

cardinal slopeforms a narrow,rounded, obscurefalseareaon eachside ofasmall,low, slightlyconvexpseudodeltidium.

Both

tlicareaandthe pseudodeltidium are scarcely observable inmost specimens.

On

casts oftheintei ior thepseudodeltidium is

more

^i)lainly

shown

(Fig-.46;),but the general surface of the exterior of the shell rounds into the false area, with scarcely

any

lineof demarcation.

A

^section of the cast of the ventral valveindicates that it

was

thin at the margin, increasing in thicknesstoward the apex,

where

it

was

asthick inproportion asin the ventralvalve of the Yorlia iraimeri.

The

cast Fig. 4c shows that on the interior of the shell there is the opening of a large foramen which taperstoa small apex,

and

that Justin advanceoftheforamen a short median depression occurs, on each side of which a slight elon-

gated tubercle arose. Outside of the tubercle a small, elongated, depressed muscle scar is seen, which

was

separated irom a deep, brrongly

marked

vascular sinus

by

a very narrow, sharp ridge.

The

vasculartrunks starton thesides of the pseudodeltidium, justbackof the foraminal opening, curving around it to the central muscle scars

and

thenextending forward tothe center of the shell. Small, round, lateralscars appearto beindicatedbackofa sharp ridge that

bounds

the posterolateralmargin of the vascular trunks.

Dorsal(brachial) valvewith a nearly transverse hingeline that is

considerablynarrower than the greatest widthof theshell.

The

car- dinal slopeforms a rather narrow area, which is broken

midway by

a low, slightly convex pseudodeltidium.

The

cast oftheinteriorshows that there

was

present in theinterior of the shell amedian ridge that extended from underthe beak forward

beyond

the center of the shell

5

oneach sideof themedian ridge, beneath the

umbonal

])ortion of the shell, a hollow occurs between the ridge

and what

apjiears to be a slightly depressed path of advance of a muscle scar.

The

features describedoccur

upon

a siliceous cast preserving the natural convexity of the shell. In a compressed specimen in the shales in which the siliceous nodules occur, the

median

ridge is well shown,

and

extends

to the center of the shell, where a pair of small anterior musclescars restagainstit. In frontof the scars the ridge sends off a

number

of tinelinesor striietoward thefrontof the shell; theantero-lateral scars occuron each side of the ridge, about one-half the distani-efrom the beak to the front margin ofthe shell.

The

posterolateralscars are alsoindicated toward the posterolateral margin.

Surface of both valves

marked by

very tine concentric stri;e

and

extremely tineradiatinglines ofgrowth. Substanceofshellcorneous.

Itis not])reservedin thesiliceous nodules, but is

shown

as a black, almostphosphaticshell in theshales.

Formation and locality.

—

^{Middle Cambrian, Coosa shales.}

^Cowans

Creek, Cherokee County,

Alabama.

(No. 2<!J:30, U.S.N.M.)

718 CAMBRIAN BRA CHIOPODA— WAL

COTT. vol. xix.

DESCRIPTION OF

TLATES.

Plate LIX.

Page.

Fig. 1. Jiihidrnsupcrhu 711

1. Dorsal Aalvc. x3.

1a. Summitviewof ventralvalve, x6.

1h. Pcsteriorviewof ventral valve, x6.

1c. Sideviewof ventral valve, x6.

2. Iphidealogani 711

2. Summitviewof ventralvalve, x8.

2a. Sideviewof ventral valve, x8.

2ft. Posteriorviewof ventralvalve, x8.

3. Iphideapealci 712

3. SummitviewofA'entralvalve, x6.

3rt. SideAuewof ventral valve, x6.

4. Iphideacrenisiria 713

\. Summitviewof ventralvalve, x6.

4a. SideA'iewof ventral valve, x6.

4ft. Posteriorviewofventralvalve, x6.

5. Iphidea alahamaensis 713

5. Summitviewof acompressedventralvalve, x6.

5a.

A

smallcompressed dorsalvalve, x6.

56. Enlargementof the surfacesideof ajjortiouof the surface of

fig. 5.

Plate LX.

Fig.1. TorJiiawanneri,newspecies 715

1. Exterior of ventral valve, withside outline, xi. Fromcast takeninnatural matrix.

1a. Naturalcastofaventral valve,withposteriorviewofarea, x3.

lb. Castofinteriorofa ventralvalve, Avith side outline, x2.

1c. Enlargementofjiosteriorhalfoffig. Ih.

Id. Cast ofinteriorofadorsal valve, Avithside outline, x2.

1c. Enlargementofthe areaandposterior portion of theinterior ofa dorsalA'alve. Fromacasttakeninanatural matrix.

2. A(Toihelc decipiens,newspecies 71(3

2. Exterior of a Aentral Aalve. x6.

3. Torkia? washingtouctisis,newspecies 715

3. Natural semcastof theinteriorof a Aentralvalve, x4.

4. Acrothelehellula,newspecies 716

4. Exterior of aA'entralvalA-e. x6. Takenfromcast ina natural matrixinasiliceousnodule.

4r(. Compressed ventralAalvein shale, x6.

4b. Naturalcastof theinteriorof aA-entralA-aU^e. x8.

4c. Interior of dorsal valve. Taken from a natural cast of the interioroccurringin a siliceousnodule, x6.

4rf. Naturalcastofan interiorof a dorsalA^alve. x6.

4e. Castof theinteriorof adorsalvalve occurringin shale, x6.

U. S. NATIONAL MUSEUM PROCEEDINGS, VOL.^{XIX PL. LIX.}

CAMBRIAN BRACHIOPODA

U. S. NATIONAL MUSEUM. PROCEEDINGS, VOL. XIX PL. LX.

CAMBRIAN BRACHIOPODA