OF CONCUOLOGY. 139 



CYCLAS, Klein. 



C. CURTA, nob. 



Description. — Equilateral, suborbicular, ventricose, concen- 

 trically finely striated; posterior end truncated, direct; dorsal 

 margins each with two or three pointed tubercles ; beaks 

 slightly prominent, acute. 



Length f inch ; height the same. 



PROTOCARDIA, Beyrich. 

 P. LIMA, nob. — pi. 10, fig. 3. 



Description. — Subtriangular, inequilateral, length greater 

 than the height, ventricose, minutely radiated ; posterior 

 margin obliquely truncated, extremity much above the line 

 of the base, obtusely rounded ; umbo rather narrow ; post- 

 umbonal slope densely radiated and tuberculated. 



Nearest in outline to P. cliversa, Conrad ; but that species is 

 smooth on the post-umbonal slope, 



CRASSATELLA, Lam. 



C. PRODUCTA, nob.— pi. 10, fig. 6. Proc. A. N. Sci., 1862, 

 p. 289. 



GOULD LA, Adams. 



G. PYGM^A, nob. 



Description. — Triangular, equilateral, with eight distinct 

 concentric ribs ; posterior hinge-margin very slightly curved, 

 the anterior straight, but slightly angular at the umbo ; 

 anterior extremity angular and situated medially to the 

 height of the valves. 



AXIN^EA, Poll. 



A. INEQUISTRIA, nob.- — pL 10, fig. 12. 



Description. — Saborbicular, slightly oblique, moderately 

 ventricose, radiating stria?, coarse, unequal towards the ends ; 

 within, the marginal teeth are concave or channelled. 



A. DUPLISTRIA, nob. — pi. 10, fig. 19. 



Description. — Subcircular, longer than high ; ventricose, 

 subequilateral, not oblique ; radii closely arranged, double or 

 grooved in the middle, except towards the ends ; within, the 

 marginal teeth small and closely arranged. 



NUCULANA, Link. 



]Sr. LiNiFERA, nob. — pL 10, fig. 8. 



Description. — Elliptical, ventricose, equilateral, concentri- 

 cally ribbed; ribs obsolete posteriorly, and remote; each side 



