150 PALEONTOLOGY. 



Imps a few other snialler ones towavd the central region; cardinal margin 

 short; hinge-area small, with apparently only a few coarse cartilage-fur- 

 rows; pallial margin strongly cre- 

 nate within; surface ornamented 

 by fine concentric striae, and a 

 few stronger marks of growth, 

 crossed by about thii-ty-five to 

 forty veiy obscm-e radiating, flat- 

 tened, or much depressed costae, 

 only separated by scarcely per- 

 g^pjj^j^ ceptible narrow or linear fur- 



Fig. 3. luterior, .and hinge of same. rOWS 



Height, 1.30 inches; breadth, 1.33 inches; convexity, 1.04 inches. 



This species is perhaps as nearly allied to A. suhimbricata, M. & PL, 

 a.s to any other Cretaceous form. It is a nuxch thicker and more gibbous 

 shell, however, with proportionally less transverse valves, and much less 

 distinctly defined costaj. It also differs in having a broader hinge-plate 

 and straighter hinge-denticles. If Poll's name Axincea should not be 

 retained for tliis genus, the name of this species here described will become 

 Pectuncuhts Wyomingensis. 



Locality and position. — East side of Cooper Creek, near Old Stage Sta- 

 tion; Laramie Plains, Wyoming Territory ; Cretaceous. 



CORBULID^. 



Genus CORBULA, Bmguiere. 



COKBULA (inult. Sp.). 

 Plato 14, fig. 2. 



Shell transversely ovate-pyriform, being gibbous in the anterior and 

 umbonal regions, and distinctly contracted, compressed, and subrostrate 

 behind; ventral margin semiovate, with the most prominent part a little in 

 advance of the middle; anterior margin truncated obliquely forward from 

 the beaks above, and somewhat abruptly rounded from near the middle 

 into the base; beak (of left valve) prominent, rather gibbous, incurved, and 



