Logan.] The Invertebrates, Fort Pierre Group. 507 



beaks nearly or quite equal, rising little above the hinge line, 

 pointed, obliquely incurved, and placed immediately over the 

 anterior margin. Surface of cast showing more or less regular, 

 rather obscure, concentric undulations, and faint tracing of radi- 

 ating markings ; the latter probably not being defined on the 

 exterior. Height, about six and fifty-hundredths inches ; length, 

 about four and ninety-hundredths inches ; convexity, two and 

 seventy-hundredths inches ; length of hinge, about two and forty- 

 hundredths inches." 



A specimen of this species was collected from the Fort Pierre 

 shales, a few miles from Atwood, in Rawlins county. The spe- 

 cies is not abundant in the Kansas area. 



Lucina occidentalis Morton. Plate cvn, fig. 3. 



Tellina occidentalis Morton, 1842, Journ. Acad. Nat. Sci. Phil., vni, p. 210, 



pi. xi, f. 3. 

 Mould of lucina Owen, 1852, Rep. Geol. Surv. Wis., Iowa, and Minn., tab. vn, 



f. 8. 

 Lucina occidentalis f M. & H., 1856, Proc. Acad. Nat. Sci. Phil., vni, 272. 

 Lucina occidentalis Meek, 1876, U. S. Geol. Surv. Terr., vol. ix, pi. xvn, 



ff. 4a, b, c, d. 



Meek's description: "Shell transversely broad oval, rather 

 thick, moderately convex; anterior side broadly rounded; 

 basal border semiovate in outline, the most prominent part 

 being toward the front ; posterior side narrower, and subtrun- 

 cated at the extremity, usually having a nearly obsolete flatten- 

 ing, extending from the beaks above the umbonal slopes 

 obliquely backward and downward to the posterior extremity ; 

 dorsal border nearly straight, or faintly sinuous, and declining 

 very slightly in front of the beaks, convex, and more obliquely 

 sloping behind ; beaks depressed, small, and nearly central ; 

 lunule lanceolate, small, and shallow, or somewhat excavated. 

 Surface ornamented by very distinct, rather regular, concentric 

 lines ; exfoliated specimens also showing obscure, radiating 

 marks on the inner laminae. 



"Length of a large specimen, one and eighty- five hundredths 

 inches ; height, one and fifty-eight hundredths inches ; con- 

 vexity, ninety-three hundredths inch. The hinge of this spe- 

 cies shows the two cardinal teeth to be rather small in the 



