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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 Litoceras Whit- 

 eavesi. It is simply a species retaining the digonal, neanic whorl 

 until a late stage, probably throughout life. 



Litoceras ? Hercules. 



Nautilus Hercules, 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 Litoceras biajigulatum 

 and the young of Litoceras insolens. 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 

 insolens. 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, n. 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 Trocholitoceras Walcotti. 



Trocholitoceras Walcotti. PL 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 



