50 
PALEONTOLOGY OF NEW YORK. 
mental grooves, diverging from the^cartilage-pit, and continuing parallel to 
the hinge-line; cartilage-pit small, triangular, placed beneath the beak. 
The largest specimen yet seen, of the left valve, is 80 mm. in height, 88 mm. 
in length, and the hinge-line 35 mm.; the distance between the strong rays 
at the basal margin is 11 mm. A specimen of medium size is 62 mm. in 
height, 72 mm. in length, hinge-line 39 mm. A young individual is 23 
mm. in height, 29 mm. in length, and hinge-line 18 mm. 
This species somewhat resembles in outline L. macrodontus, but differs in the 
surface markings, and the finer parallel teeth of the ligamental area. It differs 
from L. magnijicus, L. interradiatus, and L. cymbalon in outline; the surface of 
the latter species is similar, but more rugose. From L. Priamus it differs in 
form and surface markings. 
In comparing many specimens a great diversity in form and ornamentation 
will be observed. 
Formation and localities. In the lower and middle Chemung beds at Barker, 
Broome county; Big Flats, Chemung Narrows, and Elmira, Chemung county; 
and Franklin, Delaware county, N. Y. 
Lyriopecten Polydorus. 
PLATE VII, FIG. 25. 
Lyriopecten Polydorus, Hall. Pal. N. Y., vol. v, pt. 1 Plates and Explanations : PI. 7, fig-. 25. Jan., 18S3. 
Shell of medium size; transversely very broad-obovate; height nearly equal¬ 
ling the longitudinal diameter; pallial margins full, regularly rounded on 
the posterior side; and the anterior side of the left valve passing in nearly 
a straight line to the beak. 
Left valve depressed, nearly flat. Right valve unknown. 
Hinge-line straight, length equal to two-thirds the length of the shell, 
extending posteriorly nearly as far as the posterior margin of the shell. 
Beak pointed, directed forward, central to the body of the shell, and 
forward of the middle of the hinge-line, rising a little above it. Umbonal 
angle more than 90°. 
