CANADIAN FOSSILS. 33 



C. BlLLINGSII. 



Plate VII. Figures 5, 6. 



C. 2-3 unciale, in juventute subcylindricum involutum, in estate depresso- 

 ovale, rectius ; annulis remotioribus elevatis undulatis in dorso sinuatis ; 

 sejptis approximatis plants, siphunculo externo ; suum diametrum a 

 margine remoto. 



Synonym. — C. lamellosum, Hall, Palaeontology of New York, vol. i., 

 plate 41, figure 2 (not of DeVerneuil and D'Archiac). 



Prof. Hall's description, taken from a young and very imperfect 

 specimen, is clearly applicable ; but this species must receive a new 

 name, since the C. lamellosum, a nearly allied species from the Eifel 

 limestone, differs both in the less rate of increase in the whorl, and 

 the lamellae are much closer. The curve of the tube is also more 

 gentle. But for these proportional characters, which however are 

 quite sufficient in this genus, it would be difficult to separate the 

 Devonian species, which the Professor seems to have overlooked, as 

 he describes his fossil as new. I adopt such parts of his description 

 as are applicable to the adult form. 



Sub cylindrical when young, at a diameter of seven lines (and 

 regularly involute?), but soon attaining a more open curve and 

 becoming laterally expanded, the dorso-ventral diameter being to the 

 lateral as nine lines to thirteen, when this diameter is attained. The 

 tapering is more rapid in the young than in the adult portions. 



The lamellae are rather coarse and somewhat irregular in distance. 

 (C. lamellosum has them very close and regular.) In figure 6 they are 

 not more than a third of a line apart in the young portion (a), and 

 less than a line distant in the older portion (b), while iu figure 5 

 they are fully two lines apart in the same diameter, and become 

 closer again in the adult portion (b), where the distance is again not 

 more than a line or a line and a half.* Their course is direct over 

 the sides and inner margin, but on the outer (ventral) surface they 

 turn rapidly backward, forming a distinct sinus. They are rudely 

 fimbriated, with " transverse, undulating, squamose lamellae, abruptly 

 bent backwards on the dorsal line," and several obscure, longitudinal 

 furrows cross them. " The spaces between the lamellae are marked 



* Such a change in the ornament is not unfrequent in the Cephalopoda, and indicates 

 probably a more vigorous growth in middle age. 



C 



