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 

 Scout camp, north central sec. 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- 

 ler loc. 159-H) ; top of Pitkin, along road on east side of Fort Gibson 

 Dam, sees. 7 and 18, T-16-N, R-20-E, Cherokee County, Okla. (1 

 specimen : Waller loc. 191-H) . 



Specimens from the Pitkin Limestone collected by T. R. Waller are 

 deposited in the U.S. National Museum. His localities containing the 

 letter "H" refer to measured sections in Huffman (1958) ; those fol- 

 lowed by "M" refer to sections by Moore ( 1947) . Details are contained 

 in Waller (1962) p. 40, 129-133. 



Age. — Late Mississippian (Chester). 



COLEDIUM DUTROI Grant n. sp. 



Plate 17, figs. 1-Sb; figure 25 



Shell very large for genus, flatly to strongly biconvex ; outline trans- 

 versely subpentagonal, widest slightly anterior to midlength ; commis- 

 sure uniplicate at anterior ; fold low to moderately high, height increas- 

 ing with size of shell, crest broadly arcuate ; sulcus shallow, trough of 

 some specimens slightly convex transversely; crest of fold and mid- 

 line of sulcus indented on several specimens by narrow shallow groove, 

 producing small notch where meeting at anterior margin ; costae nor- 

 mally absent, very weak in sulcus of few specimens; posterolateral 

 edges of pedicle valve broadly flanged, covered by overlapping edges 

 of brachial valve ; valve margins protruding slightly around flanks and 

 anterior, not producing distinct stolidium; growth lines weak, fine, 

 closely and evenly spaced ; growth laminae stronger, 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 



