82 The Ottawa Naturalist. [August 



Maximum diameter of the only specimen known to the 

 writer, thirty milHmeters; that of the umbihcus, from suture to 

 suture, twenty-one millimeters. 



Red Deer River, Alberta, at Rocky Mountain Park, D. B. 

 Dowling, 1906; the small specimicn figured, which shows the 

 characters of three of the outer whorls, the nuclear ones not being 

 preserved. 



In the correspondingly early stage of growth of Peltoceras 

 athleta, as figured by d'Orbigny, the primary ribs have not begun 

 to develop well defined tubercles, and the^^ bifurcate froin near 

 the middle of each side of the outer volution. 



Dr. Waagen says that a specimen of Peltoceras annulare or 

 athleta has been found in the "vicinity of Mombas, equatorial 

 Africa," so that the genus is now known to he represented in the 

 mesozoic rocks of Europe, Asia, Africa and North America. 



As Peltoceras is regarded as an exclusively Jurassic genus, 

 it would seem inost probable that the rocks at -Rocky Mountain 

 Park from which the type of C. occidentale was collected, are of 

 Jurassic age. On purely palseontological grounds, also, it 

 would seem highly likety that those presumably Jurassic rocks in 

 Alberta which hold P. occidentale are of about the same age as the 

 coarse grits from the Crow's Nest coal fields near Fernie, B.C., 

 which hold Cardioceras Canadense, and as those Jurassic rocks in 

 the Black Hills of Dakota which hold C. cordiforme. In a Bulletin 

 of the American Museum of Natural History, New York, publi- 

 shed on December 17th, 1906, Professors Whitfield and Hovey 

 have shown that C. cordijorme is a very variable species, especially 

 in the adult state, and it is just possible that C. Canadense niay 

 prove to be only a local variety of that species. However that 

 inay be, it is abundantly clear that both C. cordiforme and C. 

 Canadcnsy' are very closely allied to the British and European 

 C. cordat'mi. 



Ottawa, Julv t2th, 1907. 



