118 University Geological Survey of Kansas. 



less convex than the other ; its anterior ear narrow, and de- 

 fined by a deep, rather sharp sinus ; posterior ear of the same 

 size and form as in the left valve. Surface ornamented in the 

 left valve with about fifteen or sixteen regular, distinct, angu- 

 lar, radiating plications separated by furrows of the same size, 

 each one of which terminates at the free border in little spine- 

 like projections, with curved-up margins ; lines of growth fine 

 on the body of the valve, but becoming more distinct and irreg- 

 ular on the ears, where there are rarely any defined radiating 

 costse. At a few distantly separated intervals there are promi- 

 nent imbricating lamellae of growth, showing the same digitate 

 margins as the free borders of *the shell. In the right valve 

 the surface markings are somewhat like those of the other valve, 

 but much more obscure, excepting on the anterior wing, where 

 there are a few more distinct radiating costae." 



Measurements : Height, 29 mm. ; length, 22 mm. ; convex- 

 ity, about 4 mm. 



Range and distribution : Upper Coal Measures ; Kansas City, 

 Turner, Eudora, Lawrence, Lecompton, Topeka. 



The strong radiating costae with the vaulted and spine-like 

 projections of the free margins and larger lamellae of growth 

 distinguish this species from all others of the genus. When 

 broken from limestone, the larger lamellae of growth are gen- 

 erally broken away. 



Aviculopecten maccoyi. Plate XIII, fig. 10. 



Aviculopecten Mccoyl Meek and Hayden, Pal. Upp. Mo., p. 50, pi. u, f. 

 9, (1864); White, U. S. Geog. Surv. West 100 Mer., iv, p. 150, pi. xi, f. 

 2a, (1877). 



Shell below medium size, moderately convex, subovate in 



outline exclusive of the ears ; hinge nearly or quite equaling 



the greatest length of the shell, slightly falling from the beak, 



which extends a trifle above it ; posterior ear larger and more 



acute than the anterior. The ventral margin is broadly 



rounded ; the posterior margin is more abruptly rounded than 



the lower anterior margin ; anterior ear separated from the 



shell by a moderately deep, rounded sinus, and from the body 



of the shell by a distinct, moderately deep, rounded depression; 



