106 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 shows as a dark line on the surface and the spondylium is often ex-

posed

by

thebreaking

away

ofthe beak.

Brachial valve

more convex

than the pedicle, the greatest depth anteriortothe middle. Slope

from

themiddle tothebeak

and margins

aboutequalexcept

on

the mesial fold; themesial foldbeginsaboutthe middle of the valve

and

has a single ill-defined furrow.

Beak

pointed

and

incurved beneaththatofthe pediclevalve.

Ordinarily the lateral slopes are without plications, but in a

few

of the largest specimens a very faint plication is developed at the an-

Fig. 23.

—

Colediumcestriensis (Snider), PitkinLimestone, Okla. (Waller loc.

169-H, unit 34),

USNM

^142105. Longitudinal section through midline, X5, showingprofilesofcamarophorium,intercamarophorialplate (lined), hingeplate,

and septumofspondylium.

terior

margin

nearthe mesialfold

on

the brachial valve

and

a corre- sponding

furrow

is

shown on

the ventralvalve.

Surface

markings

consist of faintconcentric lines ofgrowth.

Supplementary

descriptive remarks.

— ^Spondylium

ⁱⁿ pedicle valve sessile at

extreme

apex, then elevated

on low median septum

; trough of

spondylium

extending anteriorly about one-third length of valve,

septum

continuing nearly to midlength.

Camarophorium

in brachial valveextending tomidlength of shell, about one-third length ofvalve,

septum

supporting

camarophorium

slightly shorter; trough strongly curved ventrally (longitudinally), producing very high

septum

be-

tween

it

and

stronglycurved valve floor; hinge plate short,connected to posterior part of

camarophorium by

thin intercamarophorial plate.

Lectotype {here designated).

—

^{Snider, 1915, pi. 4, figs.}

^15-18

(Univ. Chicagocoll.).

Growth. — ^The

patterns of

growth

in this species are typical forthe genus, with increase in width varying narrowly along a straight line relative to increase in length,

and

increase in thickness slightly ac- celerated (fig.24).

The

slopeofthe length-width line

shows

that short Fig.24.

—

^{Scatterdiagrams} ofdimensionsofColediumcestriensisfromalllisted localitiesinthePitkinFormation, Okla.

o o o

°o ^o

o

o o o

o ° °°o

o o

8 £0

o o o

^o,o

LENGTH (MM)

I I I I I I I I I »

3 4 5 6 7 8 9 10

II

12 13

o o

o o o

^<*

o O

Be

o o8 o

o

If

12- 13- 14-

Fig.24.

—

(Seeoppositepagefor legend.)

°8o°

107

108

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL. I48 Table 19. Measurements of Coledium cestriensis from the Pitkin Limestone in

Oklahoma

Measurements,inmillimeters

USNM

No.

NO.2

BRACHIOPOD SUPERFAMILY STENOSCISMATACEA GRANT

IO9 Gibson, Okla. (1 specimen

USNM ^142106);

Pitkin-Fayetteville boundary,

on Oklahoma Highway

10, in sees. 21

and

29,

T-15-N, R-

20-E, 4

miles southeast of Fort Gibson, Okla. (5 specimens:

Waller

loc.

169-H)

; Pitkin Limestone, 12-20 feet

below

top, in

abandoned Keough

Quarry, along

Highway

80, 1.5 miles north of Fort Gibson, in

SW.J4

sec. 25,

T-16-N, R-19-E, Cherokee

County, Okla. (41 specimens:

Waller

loc.

69-M)

; Pitkin Limestone, in bluff at

Boy

Scoutcamp, northcentralsec. 19,

T-16-N, R-23-E, Cherokee

County, Okla. (8 specimens:

Waller

loc.

201-H)

; Pitkin (displaced blocks) at

Elk

Creek, sees. 5

&

8,

T-14-N, R-23-E,

Okla. (1 specimen:

Wal-

lerloc.

159-H)

; topofPitkin, along road

on

east side ofFort

Gibson Dam,

sees. 7

and

18,

T-16-N, R-20-E, Cherokee

County, Okla. ₍₁ specimen:Wallerloc.

191-H)

.

Specimens from

the Pitkin

Limestone

collected

by

T.R.

Waller

are deposited inthe U.S. National

Museum. His

localities containing the letter

"H"

refer to

measured

sections in

Huffman

(1958) ; those fol-

lowed by "M"

refer tosections

by Moore

(1947)^.Details arecontained in

Waller

(1962) p.40, 129-133.

Age. —

^Late Mississippian (Chester).

COLEDIUM DUTROI

^{Grant n. sp.}

Plate17, figs.1-Sb;figure25

Shellverylarge forgenus, flatlytostronglybiconvex;outlinetrans- verselysubpentagonal, widest slightly anterior to midlength;

commis-

sure uniplicateatanterior;foldlowtomoderatelyhigh, height increas- ingwith sizeof shell, crestbroadly arcuate; sulcus shallow, trough of

some

specimens slightly

convex

transversely; crest of fold

and

mid- lineofsulcusindented

on

several specimens by

narrow

shallowgroove, producing small notch

where

meetingat anterior

margin

; costae nor- mally absent, very

weak

in sulcus of

few

specimens; posterolateral edges of pedicle valve broadly flanged, covered

by

overlapping edges ofbrachialvalve;valve

margins

protrudingslightly

around

flanks

and

anterior, not producing distinct stolidium;

growth

lines weak, fine, closely

and

evenly spaced;

growth

laminaestronger,especially at ante- rior,widely

and

irregularly spaced.

Pedicle valve evenly

and

moderately strongly

convex

longitudi- nally, flatly

convex

transversely, thickest in

umbonal

region; beak thick, only slightly attenuate, erect to slightly incurved, not pressed tightly against brachial

umbo,

leaving

room

for small

foramen

; shape of

foramen and

possibility of modification

by

deltidial plates not ob- served.

Brachial valve strongly

convex

transversely, less strongly

convex

no SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL. I48 longitudinally along fold, greatest swelling in

umbonal

region;

beak

bluntly pointed,

apex

normallyhidden beneathpediclebeak.

Pedicle valveinteriorwithdental plates joiningabovefloor to

form

rather shallow spondylium, supported for entire length

by median septum

(spondylium not sessile in

apex

of valve), height of

septum

increasinganteriorly,

becoming

very highforgenus,continuinganteri- orlyaboutone-third lengthof valve.

Brachial valve interior with short undivided hinge plate; cardinal process

formed by

slight swelling of

apex

ofplate,

weakly

scored lon- gitudinally for attachment of diductor muscles;

camarophorium

ele-

vated

on low median septum

duplex in apex, height of

septum

in- creasing greatly

toward

anterior; sides of

camarophorium

reaching nearlytoundersideofhingeplate, midlineconnectedto plate

by

inter- camarophorial plate extending anteriorly slightly

beyond

hinge plate

;

septum

of

camarophorium

extendinganteriorlyabout one-fourthlength of valve, crest of

camarophorium somewhat

longer; crura extending

forward from

anterior edge of hinge plate, curved ventrally to follow contour of crest of

camarophorium;

muscles

and

pallial

marks

not observed.

Holotype.— USNM

142109,^pi. 17,fig.2.

Comparisons.

— Coledium

dutroiisthe largest

known

species of the genus, comparable in size to

many

species of the normally larger Stenoscisma. Inadditiontoits size, itischaracterized

by

^itshigh con- vexity (in large adults) broad fold that

becomes

high in adults

and

has a

median

groove in about half the

known

specimens, its broad

Fig. 25.

—

Coledium dutroi n. sp., Mississippian Ladrones Ids., Alaska, trans- versesections X4,originallength20.0

mm. USNM

142110, distancesgivenfrom pediclevalve beak.

A.2.5

mm.

^: cardinalprocessdistinct, septumofspondyliumhigh. B.2.8

mm.

:

spoon ofcamarophorium separate fromhinge plate, septumduplex with wedged

insertion intovalve floor. C. 3.0

mm.

^: intercamarophorial plateduplex. D. 3.4

mm.

E. 4.0

mm.

^: crura and intercamarophorial plate anterior to hinge plate

;

spondyliumhigh.

NO. 2

BRACHIOPOD SUPERFAMILY STENOSCISMATACEA GRANT

III