CEPHALOPODA— ORTHOCHOANITES. 



71 



Beekmantownian (Fort Cassin beds) of Lake Champlain region. 

 69. S. cassinense (Whitfield). Ordovicic. 



More quadrangular in section, with flattened venter; sutures 

 straight; whorls less rapidly enlarging. 



Occurs with the preceding. 



XXII. Trocholites Conrad. 

 Living chamber always in contact with preceding whorls ; whorls 

 in section always wider than high ; aperture expanded with ventral 



/ 



% d 



Fig. 1282. Trocholites ammonius, with section. (After Hall, Pal. N. Y., I.) 



sinus; sutures simple or slightly lobed; siphuncle dorsal or sub- 

 dorsal. Ordovicic. 

 70. T. ammonius Hall. (Fig. 1282.) Ordovicic. 



Fig. 1283. Trocholites pi anorbiformis, X /^- (After Hall, Pal. N. Y., I.) 



Regularly enlarging, slightly impressed; sutures with gentle, 

 lateral saddle ; siphuncle propriodorsan in young, centrodorsan in 

 adult; surface rough, fretted. 



Trenton and Utica of New York. 



