300 PALEONTOLOGY OF NEW YORK. 



Beaks sub-anterior, small and closely appressed ; umbo prominent ; umbo- 

 nal ridge more or less strongly defined and distinctly angular, extending to 

 the post-basal extremity. 



Test of moderate thickness, marked by regular concentric thread-like 

 striae, which are abruptly recurved on the umbonal ridge ; anterior muscu- 

 lar impression deep and strong. The pallial line extends parallel to the 

 ba-sal margin, and abruptly recurves over the umbonal ridge, terminating in 

 a large shallow posterior muscular scar upon the cardinal slope. The hinge 

 is furnished with a strong triangular fold beneath the beak of the left valve, 

 and a corresponding depression in the right valve. 



Three specimens measure respectively 90, 61 and 49 mm. in length, and 

 49, 39 and 28 mm. in height. 



This species closely resembles G. Hamiltmensis, but differs principally in its 

 proportionally shorter form, more convex basal margin and more direct umbo- 

 nal ridge. 



Formation and localities. In the Hamilton group, Fultonham and Be.ar's 

 gulf, Schoharie county; Kelloggsville, Cayuga county, and on the shore of 

 Cayuga lake, N. Y. 



GoNioPHORA Ida. 



PLATE XLU, FIG. 13; AND PLATE LXV, FIG. 20. 



Sanguinolites Ida, Hall. Pi-elim. Notice Lamellibranchiata, 2, p. 43. 1870 



Pal. N. Y., vol. V, pt. 1. Plates and Explanations : PI. 6."), fig. 20. 1883. 



(( «( 



Shell of medium size, elongate sub-elliptical ; length about two and one-half 

 times the height ; basal margin regularly curved ; posterior margin very 

 obliquely truncate. Cardinal line straight, less than half the length of the 

 shell. Anterior end gently declining from the beak, narrow, and abruptly 

 rounded at the extremity. 



Valves regularly convex; cardinal slope depressed, and abruptly concave 

 just above the umbonal ridge. 



Beaks at about the anterior third, small, appressed, slightly projecting 



