42 
NAUTILOIDEA. 
bilicus, they become quite obsolete ; the young shell is almost 
smooth. The entire surface of the test is covered with very fine 
transverse lines both on the ribs and the interspaces, and there are 
Tig. 4. 
Trochoceras Halli. — a, lateral view ; h, ventral or peripheral view, showing the 
deep sinus formed by the annulations. Drawn from a specimen in the 
Collection. Natural size. 
also obscure traces of longitudinal lines. The septa are a little 
more than 1 line apart, where the shell has a ventro- dorsal diameter 
of 6 lines. The siphuncle is not seen. 
Remarks. On looking at the table of references above, it will be 
observed that T have incorporated in the present species certain of 
the forms figured by Hall under the name of “ Lituites” undatus. 
The others figured by that author upon the same plate, and also the 
one upon plate xiii. (bis), belong to the genus Trocholites, as pointed 
out by Hyatt ’ . 
It was suggested many years ago by Professor E. J. Chapman 
of Toronto (Canada West), that the specimens obtained by the 
Geological Survey of Canada, from the Black River Limestone, at 
Lorette, near Quebec, and known under the name of Lituites undatus, 
^ Proc. Boston Soc. Nat. Hist. 1883, vol. xxii. p. 267. It is singular that 
this author should have overlooked the obvious distinctness of some of these 
forms from the rest, and that he should have included them all in Trocholites. 
2 Ann. & Mag. Nat. Hist. 1857, 2nd series, vol. xx. p. 117. 
