480 
Nautilus versutus. The sides, however, until a late stage are 
angular, forming a truly digonal whorl with broad rotund abdomen. 
The ventral saddle is more plainly marked and more prominent, 
and the whorls more numerous at the same age. ‘There are saddles 
at the abdominal angles and lateral lobes; the dorsal sutures were not 
seen. The contact furrow is about the same as in Lz¢toceras Whit- 
eavest. It is simply a species retaining the digonal, neanic whorl 
until a late stage, probably throughout life. 
LITOCERAS ? HERCULES. 
Nautitus Hercutes, Bill. (Rep. Geol. Surv. Can., 1856, p. 306). 
Loc., Charleton Pt., Anticosti. 
This smooth shell found in the Lower Silurian of Anticosti has 
the digonal form of whorl similar to that of Lztoceras biangulatum 
and the young of Léteceras tnsolens. It is, however, a very much 
larger and more rapidly growing shell. The sutures have ventral 
median saddles, and on either side ventral lobes as in the young of 
znsolens. ‘The abdominal angles have saddles and there are well- 
marked lateral lobes rising to slight saddles at the lines of involu- 
tion. The diameter of Billings’ specimen was 6% inches with 
incomplete living chamber. 
Trocholitoceras, 0. g. 
This genus has been framed to include forms which are essentially 
similar to Trocholites, but have the siphuncle ventrad of the centre 
in the earlier substages of development. 
The forms stand in development and adult characters between 
Litoceras and Trocholites. 
Type is Zrocholitoceras Walcott. 
TROCHOLITOCERAS WALCOTTI. PI. vi, Figs. 12-20. 
Loc., Fort Cassin. 
The series of sections drawn in Figs, 14-19, Pl. vi, gives the his- 
tory of the development of the shell and siphuncle in this interesting 
species. ‘The first sectional cut (Fig. 14, Pl. vi) shows the round 
ananepionic volution, the umbilical perforation and below this the 
paranepionic volution with the siphuncle ventro-centren, and the 
outline beginning to broaden and approximating to the kidney- 
shape, above the round ananepionic section is the ananeanic whorl 
with the siphuncle centrodorsen, It will be observed that this section 
