60 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



BELLEROPHON OTSEGO (n.s.). 



Shell subglobose. Body-volution ventricose, somewhat trilobate, 

 the middle much wider than the lateral lobes, gradually spread- 

 ing towards the aperture, which is moderately expanded and 

 somewhat deeply sinuate in front. 



Surface marked by regular transverse arching strise, which have a 

 retral curve upon the dorsum. Dorsum marked by a narrow band, 

 enclosed between two sharp elevated strise, which are distant 

 from half a line to a line, varying with the size of the shell. 



The lateral lobes are separated from the central or main part of the vo- 

 lution : this character, with the comparatively wide dorsal band limited by 

 thin sharp striae, are characteristic features. 



Geological formation and locality. In the coarse sandy shale of the 

 Hamilton group in the south part of Schoharie county, and in Otsego county. 



BELLEROPHON THALIA ( n. s.). 



Shell ovoid or subspheroidal. Volutions rotund, the last one gra- 

 dually expanding and becoming ventricose towards the aperture, 

 which is somewhat orbicular, with a deep sinus at the anterior 

 margin : umbilicus closed. 



Surface with liue even concentric strise. Dorsum, in the cast, marked 

 by a sulcate carina. 



This species occurs as casts of the interior, and retaining portions of the 

 shell showing a surface-marking similar to B, hilohatus of the Lower Si- 

 lurian rocks ; and the shell has nearly the same form and proportions, with 

 the exception of the carinate dorsum. 



Geological formation and locality. In the shales of the Hamilton group 

 at York in Livingston county, and at Pratt's falls in Madison county, N.Y. 



GENUS PHRAGMOSTOMA ( Hall). 



PHRAGMOSTOMA NATATOR. (c \jl,I^Jlf 



Bellerophon expansus ? Geol. Rep. 4tli District New-Tork, 1843, p. 244, f. 3; p. 248. 

 Is'ot Bellerophon^xpansus of Sowerby. 



This species shows a widely expanded aperture, with a deep si- 

 nuosity in the anterior margin : the sides of the shell are strongly 

 undulated or wrinkled. The dorsum is marked by an obtuse angular 



[ September, 



