4 
PALEONTOLOGY OF NEW YORK. 
“ Monotisprinceps. —Shell convex, depressed; ear small, emarginate; radiating 
striae numerous; rugose, profound. Length about 3 inches. 
“ Locality, Cazenovia.” 
Mr. Conrad’s description of Avicula parilis is as follows {Jour. Acad. Nat. Sci. 
Phila., Yol. VIII, p. 239. 1842): 
“ Avicula parilis, pi. 12, fig. 9.—Upper valve flat; 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 flat 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 pecteniformis. 
PLATE I, FIG. 9. 
Avicula pecteniformis, Conrad. Journal Acad. Nat. Sci. Phila., vol. 8, p. 240. 1842. 
Aviculopecten pectenifoimis, (Conrad) Hall. Pal. N. Y., vol. v, pt. 1. Plates and 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. 
