158 PALEONTOLOGY. 



base forming a long, semi-elliptic curve; posterior extremity more narrowly 

 and less regularly rounded than the other, apparently slightly bent to the 

 left; dorsal margin declining very slightly, with convex slopes, both in front 

 and behind the beaks ; beaks very nearly central and inconspicuous, being 

 depressed and compressed. Surface of casts smooth, but probably on well- 

 preserved shells marked with fine concentric striae. Hinge and interior 

 unknown, with the exception of some appearances of lateral teeth seen in 

 casts. 



Length, 0.86 inch; height, 0.44 inch; convexity, 0.10 inch. 

 This little shell has the general form of Tellina, or Ahra, but without 

 seeing the hinge and interior it is impossible to determine whether it may 

 not belong to some allied, but distinct, group. It is a more depressed shell 

 than T. scitula^ M. & H., or any of the other species from the Cretaceous 

 rocks of the Upper Missouri, and I have been unable to identify it with any 

 of the known American or foreign species. Perhaps the most nearly allied 

 American fossil species yet known is Mr. Gabb's T. Ashburnerii (from 

 division A of the California Cretaceous series), which, however, is a pro- 

 portionally higher (wider) shell, with much less depressed and more angular 

 beaks. 



Locality and position. — Whitish sandstone of East Canon Creek, Wasatch 

 Range, upper part of series ; Cretaceous. 



VENEEIDiE. 



Genus CYPRIMERIA, Conrad. 



Cyprimekia? subalata, Meek. 



Plate 15, fig. 7. 



Cyprimeria stibalaia, Meek (1873), Hayden's Sixth Eeport U. S. Geol. Survey of the 

 Territories, 476. 



Shell transversely broad-subovate or subelliptic, strongly compressed; 

 extremities rather narrowly, and nearly equally rounded; basal margin 

 forming a regular semi-elliptic curve, being most prominent along the mid- 

 dle, and rounding up gradually and equally int^o the anterior and posterior 

 lateral margins; dorsal margin sloping from the beaks, the posterior slope 

 being more convex in outline than the anterior; beaks small, scarcely pro- 



