396 PALEONTOLOGY OF NEW-YORK. 



• The larger well-marked individuals have a length of about one inch ; 

 and a single specimen, apparently of this species, is nearly two inches 

 long. 



In the young or half-grown shells, the valves are moderately conyex 

 and th"e beak scarcely incurved, while there is no perceptible truncation 

 in front. The flattening of the umbo and umbonal slopes are not con- 

 stant characters, and we have regularly ovate forms with every part 

 limited by curved lines. 



I have received from Dr. G. A. Williams, formerly of Hardy county, Virginia, 

 several casts of a species of this genus, which I have referred to this. One of 

 those figured upon the plate is proportionally more elongate than the New- York 

 forms ; but the shell has been abruptly incui-ved on the umbonal slopes, flattened 

 on the lower part of the ventral valve, and obliquely subtruncate in front. 



Geological formation and localities. This species occurs in the Hamilton group 

 on the shores of Seneca and Canaudaigua lakes, at Moscow, York and Geneseo in 

 Livingston county, and at Pavilion in Genesee county, New-York. 



Cryptonella iphis (n. s.). 



PLATE LXI. 

 Shell elongate, subcylindrical. 

 Ventbal valve more convex than the dorsal, regularly arcuate from beak 



to base, the greatest convexity about the middle of its length, abruptly 



rounded or subtruncate in front. Beak much extended beyond that of 



the opposite valve, and slightly arcuate. 

 Dorsal valve somewhat depressed-convex in the middle, and shortly 



curving to the margins; the upper two-thirds of the length of the 



valve almost equally convex. 

 Sckface concentrically striated, with a few strong undulations towards 



the front, in the cast. Shell-structure punctate. 



Length one inch ; width less than three-fourths of an inch. 



The specimen is almost an entire cast, and is referred to the Genus Crypto- 

 nella from the elongate form, moderately incurved beak, and character of mus- 

 cular impressions. The punctate, structure of the shell indicates its position among 

 the Terebratulidas. 



Geological formaiion and locality. This shell occurs in the Corniferous lime- 

 stone, near Cayuga in Canada "West. 



