4 PALEONTOLOGY OF NEW YORK. 



" Monotis princeps. — Shell convex, depressed; ear small, emarginate ; radiating 

 .stria; numerous; rugose, profound. Length about 3 inches. 

 " Locality, Cazenovia." 



Mr. Conrad's description of Avicula parilis is as follows {Jour. Acad. Nat. Sci. 



Phila., Vol. VIII, p. 239. 1842): 



" Avicula parilis, pi. 12, fig. 9. — Upper valve fiat; lower valve plano-convex ; 

 surface with numerous, equal, filiform, prominent radii; wings angulated at 

 tip, the anterior one most acute, and nearly equal in length to the posterior 

 wing; apex not elevated above the hinge line; anterior, posterior, and basal 

 margins forming an uninterrupted arched or rounded outline. 



" Locality, Cazenovia, Madison county, New York. Upper Silurian shale. 



" A beautiful and common species, the larger valve much resembling a 

 Pecten. 



"The Monotis princeps, of the Geological Reports of New York, is probably 

 the same shell. 



" The fiat valve is represented on the plate." 



Formations and localities. In limestone referred to the age of the Upper 

 Helderberg group (Corniferous limestone), at Sandusky, Delaware, and near 

 Columbus, Ohio; and also at the Falls of the Ohio. 



In the coarser shales of the Hamilton group, at numerous localities in the 

 eastern and central portions of the State ; in the upper soft calcareous shales 

 of the group at Moscow, Livingston county, N. Y., and very rarely in the 

 western extension of the group. 



AVICULOPECTEN PECTENIFORJIIS. 



PLATE I, FIG. fl. 



Avicula peett nifnrmis, Conrad. Journal Acad. Nat. Sci. Phila., vol. 8, p. 240. 18-4'J. 

 Aviaulopecten peeteniformis, (Conrad) Hall. Pal. N. Y., vol. v, pt. 1. Plates ami Explanations : PI. 1, fig. 



9. Jan., 1883. 



Shell sub-ovate oblique to the hinge-line ; length equal to the height ; anterior 

 and basal margins regularly rounded, the body of the shell extending in a 

 nearly straight line from the postero-lateral margin to the beak. 



Left valve convex, reaching its greatest convexity at about one-third the 

 length of the valve from the beak. 



