TRENTON CONGLOMERATE OF RYSEDORPH HILL 29 



an undate appearance. This feature is shown by all specimens, 

 and is, therefore, evidently quite constant. It constitutes a 

 specific difference from other species of Ctenodonta, of which 

 0. s i m i 1 i s Ulrich, from the upper Lorraine beds of Minnesota, 

 is evidently very similar in outline, character of beak, etc. to the 

 form from Rysedorph hill. As, however, the internal characters 

 have not been elucidated, the description of the species is 

 properly deferred till more complete material can be obtained. 

 (Group 5) 



GASTROPODA 



PROTOWARTHIA ITlrich 



Protowarthia cancellata Hall sp. 



Belle rophon bilobatus Hall non Sowerby. Pal. N. Y. 

 1847. 1:184 



Belle rophon cancellatus Hall. Pal. X. Y. 1847. 

 1:307 



The fossil referred by Hall to B e 1 1 e r o p h o n bilo- 

 batus Sowerby occurs quite frequently in well developed speci- 

 mens in the black compact limestone pebbles. Ulrich, main- 

 taining that the American and the European form are specific- 

 ally distinct, doubts whether the latter occurs In America, 

 though its name has entered so largely into the American geo- 

 logic literature; and, as he believes that Hall's B. bilobatus 

 from the Trenton and Lorraine beds is identical with the same 

 author's B. cancellatus from the Lorraine, he applies the 

 latter name to this important Trenton form, making it at the 

 same time the type of a new genus. Some of the specimens of 

 the Rysedorph hill conglomerate by their more angular beak and 

 the outline of the apertural lobes approach forms which for- 

 merly were also referred to B. bilobatus, but have been sep- 

 arated by Ulrich as Protowarthia rectangularis. 



Belle rophon bilobatus was known to Hall only from 

 the Trenton, Utica and Lorraine beds of New York. It pos- 

 sesses the same range in Canada, while in the west it has been 

 found to appear in the Black river beds and to rise above the 

 Lorraine into the Richmond beds. (Group 5) 



