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NEW YORK STATE MUSEUM 



from Fort Cassin. that appears to belong to this species, having 

 similar sutures, form of whorl and involutions." 



E . Virginia n u s is characterized as having " more cylindrical 

 whorls and more numerous and straighter sutures at all stages than 

 in k e 1 1 o g g i /' We have not observed any adult specimens ref- 

 erable to this species in the collections from the Champlain basin. 



Genus tarphyceras Hyatt 



This genus has been separated from Eurystomites Schroder by 

 Hyatt [1894, p. 433]. The latter author states the relation of the 

 two genera as follows : 



This genus has heretofore been confounded with Eurystomites 

 by Schroder, the species being found together and resembling each 

 other in general aspect. It differs, however, from that genus in 

 having a more discoidal form, more numerous and more slowly 

 growing whorls, in length of living chamber, in form, aperture and 

 other characters. 



As to the differences in the length of the living chamber, it has 

 been asserted later on [p. 442] by Hyatt that the living chamber 

 in Eurystomites is very variable in length, shorter than in Tarphy- 

 ceras in the adult E . ke 1 1 o gg i , and in the aged specimens very 

 long. The length of the living chamber can, therefore, hardly be 

 relied upon for generic distinction. 



The aperture of Eurystomites has prominent lateral crests, at least 

 in E . k e 1 1 o g g i , while in Tarphyceras the aperture is more as 

 in Trocholites and has a deep broad hyponomic sinus encroaching 

 upon the lateral zones ; the latter having but low and broad crests. 

 The amount of involution is also greater in the ephebic stage of 

 Eurystomites than is usual in Tarphyceras, and the contact furrow 

 is deeper. 



The genus Tarphyceras can be truly considered as attaining the 

 climax of its development in the Beekmantown formation, for there 

 are here described from the Fort Cassin beds no less than four species 

 ( one of them new ) , while another one ( T. f a r n s w o r t h i Bill.) 

 is cited by Hyatt from Philipsburg in the Champlain basin. Three 

 more species occur in Newfoundland, one in Lexington Ya.. and 

 one, doubtful in its generic position (T. con volvcns, Angelin 

 and Lindstrom ) in Europe. We have added here a species from the 

 Chazy beds ( T . m u 1 t i c a m e r a t u m ) , which in some char- 

 acters appears already as a phylogerontic form [see p. 473]- 



