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 ravs 

 at the basal margin is 11 mm. A specimen of medium size is 02 mm. in 

 height, 72 mm. in length, hinge-line 39 mm. A young individual i> 23 

 mm. in height, 29 mm. in length, and hinge-line 18 nun. 



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. magnificus, 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 Elniira, Chemung county; 

 and Franklin, Delaware county, N. Y. 



LVRIOPECTEN POLYDORUS. 



PLATE VII, FIG iV 



Li/ruipecten Polydorux, Hall. Pal. X. V.. vol. v. pt. 1 Plates and Explanations : PI. 7. ti;_'. :>">. Jan.. 1883. 



Shell of medium size; transversely very broad-obovate ; height nearly equal- 

 ling the longitudinal diameter ; pallia! 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 Hat. 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 binge-line, rising a little above it. Umbonal 

 angle more than 90°. 



