193 



CYRTOCERAS ALETHES. (N. sp.) 



Fig. 177. 



Fig. 178. 



Fig. 179. 



Fig. 177. Cyrtoceras Alethes. a, ventral view ; 6, section ; c, side. 

 ] 78. C. Syphax. Ventral view. 

 179. Cyrtocerina Mercurius. Side view. 



Description. Shell small, slender, gradually tapering, gently curved ; 

 section elliptical, the dorso-ventral diameter being about one-fourth, or 

 one-third greater than the lateral ; septa about fourteen or fifteen to the 

 inch ; siphuncle small, in contact with the shell on the ventral side. 

 Chamber of habitation proportionately very deep. Surface unknown. 



The only specimen collected is 13 lines in length ; dorso-ventral dia- 

 meter at the aperture 5 lines ; lateral diameter 3J lines ; dorso-ventral 

 diameter at the smaller extremity of the specimen 3 lines ; depth of 

 chamber of habitation 9 lines. It is possible that the specimen may be a 

 little distorted by lateral compression. The diameter of the siphuncle is 

 about half a line, and its section is not quite circular, being flattened on 

 the ventral side, where it is in contact with the shell. The curvature of 

 the ventral side, so far as it can be ascertained, for the portion preserved, 

 is that of a circle with a radius of 15 lines. It is probably more sharply 

 curved near the apex. 



This species differs from all the ordinary forms of this genus found in 

 the Lower Silurian rocks of Canada in its slender proportions and compa- 

 ratively distant septa. A small species, C. exiguum, occurs in the Black 

 River limestone somewhat like it, but with a circular section. 



Locality and formation. Point Ed vis ; in limestone No. 2. Quebec 

 group. 



Collector. E. Bell. 



