No. 136.] 109 



This is a more robust species than the T. annulatum : it is readily dis- 

 tinguishable in the absence of annulations, and in the dorsal position of 

 the siphuncle, while the umbilicus is proportionately narrower and 

 deeper. 



Geological formation and locality. In the Schoharie grit ; Helderberg 

 mountains and Schoharie. 



GOMPHOCERAS EXIMIUM (n.s.). ^ 



Shell large, the outer chamber gradually contracting from the 

 last septum, and tapering in about the same degree in the 

 opposite direction : section elliptical. The twelve chambers 

 preceding the outer one measure three inches in length ; the 

 greatest diameter at the outer section being three and a half 

 inches, and, at the distal section, two and a half inches. 



There are about three inches of the outer chamber preserved in the 

 specimen. The entire length of the specimen is more than six inches^ 

 •the ^eater diameter about three inches, and the lesser diameter two 

 inches. It may have suffered accidental pressure in some degree; but 

 it is evident, from the prevalent form, that the shell has been originally 

 elliptical in section. 



Geological formation and locality. In the Upper Helderberg limestone: 

 Black Rock, New- York. 



