TRIASSIC FOSSILS. 29 



CORBULA, Brug. 

 C. Blakei, n. s. 



PL 5, Pig. 24. 



Shell (right valve) subquadrate, convex; beak nearly central; 

 umbone large, prominent. Anterior margin regularly rounded ; 

 posterior abruptly truncated. Umbonal ridge angular, distinct. 

 Posterior to this ridge the surface slopes at an abrupt angle to 

 the margin of the shell. Surface ornamented by irregular con- 

 centric lines. Length, .46 inch. "Width from beak to base, .3 

 inch. Depth of valve, .12 inch. 



A single specimen only has been found. Collected by Mr. G. Blake in the Hum- 

 boldt Mining Region. 



MYTILUS, Linn. 

 M. Homfrayi, n. s. 



PI. 6, Pig. 25. 



Shell thick, oblique, convex; cardinal margin arched, poste- 

 rior end convexly and obliquely truncated, anterior margin very 

 slightly convex. Surface marked only by lines of growth. 



Figure, natural size. 



Locality: Two specimens from Dun Glen, Sierra District, Humboldt County, 

 Nevada Territory, associated with Nautilus multicameratus. Collected by Mr. 

 Homfray. 



This shell belongs to the type of M. vetustus, Goldf., of the Muschelkalk, but is 

 sufficiently distinguished by its outline, being longer, more slender and more 

 oblique. It is also somewhat less convex than that species. 



AVICULA, Klein, Lam. 

 A. Homfrayi, n. s. 



PL 6, Fig. 26. 



Shell trigonal, oblique; left valve convex, right valve un- 

 known. Cardinal and posterior margins nearly straight, uniting 



