140 CONTRIBUTIONS TO CANADIAN PALiEONTOI.OGT. 



larger but slightly distorted specimen, tlie maximum diameter is not 

 quite seventy mm. 



Variety lenticulare. (Figs. 3 and 3 a.) Shell sublenticular, but 

 always a little depressed in the umbilical region : greatest breadth or 

 thickness equal to one-third of the maximum diameter : umbilicus 

 very narrow and indistinctly defined, in some specimens almost closed : 

 perijjhery acutely angulated : aperture mucli narrower laterally than 

 in the typical form. 



Surface neai-ly smooth, marked only with fine radiating striic, which 

 are doubly flexuous on each of the sides and produced into a series of 

 obtuse, beak-like projections which arch forwards on the jjeriphery. 



Sutural line apparently similar to that of the tyj)ical form. 



Dimensions of the largest specimen of this variety known to the 

 writer : maximum diameter, sixty millimetres ; greatest breadth of 

 the same, twenty mm. 



It is only proper to add that the typical and convex form and the 

 flattened variety lenticulare are connected by numerous intermediate 

 gradations both in form and sculpture. 



Liard Paver, about twenty-five miles below Devil's Portage, also 

 about thirty miles below the same portage, R. G. McCounell, 1887. 

 At the first mentioned locality five specimens were collected, of various 

 sizes, most of which belong to the typical and convex form of the 

 species. At the second locality indicated, seventeen sjDccimens were 

 collected of all sizes, varying from eight to about sixty millimetres 

 in their greatest diameter. Eight of these have a maximum diameter 

 of more than an inch and a half, and of these four belong to the typical 

 form and four to the variety lenticulare. 



The genus Popanoceras was first proposed and its characters defined 

 by ProfesBOi- Hyatt, in 1884, in the twenty-second volume of the Pro- 

 ceedings of the Boston Natural Plistory Society, on page 33*7. The 

 types of the genus ai'e there stated to bo the Goniatites Kingianus, G. 

 Koninckianus and G. Soboleskyanus of Murchison, Do Verneuil and 

 Keyserling, fi-om the Dyas (or Permian formation) of Ruswia. In 

 1886, on pages 67-72 and plates 14 and 15 of his " Arktische Triasfau- 

 nen," Mojsisovics described and figured four named* and two unnamed 

 additional species from the Upper Trias of Spitzbergen. The present 

 species, which the writer has much pleasure in associating with the 

 name of its discoverer, may be readily distinguished fi-om the whole 

 of these previously characterized foi-ms by its much larger size and 

 more especially by its more or less convexly sublenticular form and 

 very distinctly angulated periphery. 



* P. Hyutti, P. Tardli, P. Malmi/reni und P. Vernauli. 



