200 NEW YORK STATE MUSEUM 



the equilateral division of the shell, as the distinguishing feature of the 

 species. 



Dimensions. An average specimen has a length of 26 mm ; and hight 

 of 20 mm. 



Habitat. Genesee province ; Chautauqua subprovince. Known only 

 from the shales at Pontiac, Erie co. 



Ontaria accincta sp. nov. 



Plate 8, fig. 22-25 



Shells small for this genus but slightly convex, with subcentral beaks. 

 Outline circular. Cardinal line short and straight, the curve sometimes a 

 little broader anteriorly. Surface smooth or with traces of concentric lines 

 about the margin and an occasional circular ridge or wrinkle ; no radial 

 lines visible. The embryo shell is distinctly set off from the rest of the 

 valve by a deep cincture, and this feature seems to be always present and 

 may be construed as a characteristic of the species. 



Dimensions. Length and hight 7-8 mm. 



Habitat. Genesee province ; Naples subprovince. Cashaqua creek. 



Observations. A considerable number of shells from the same locality 

 have the above features and attain about the same dimensions. The 

 peculiar prominence of the prodissoconch seen in all these appears sporadi- 

 cally in adult specimens of O. suborbicularis. We believe however 

 that it persists in all the shells of this more westerly form and, together 

 with the other surface characters, will serve to keep it distinct therefrom. 



Ontaria clarkei Beushausen (sp.) 



Plate 7, fig. 10-20 



Cardiola clarkei Beushausen, Abhandl. der konigl. Preuss. Geolog. N. F. 1885. 

 Heft 17, p. 347, pi. 36, fig. 10a 



It is a rather singular incident that Beushausen under the above name 

 should have described from a single valve a species which is of so frequent 

 occurrence in the New York Intumescens fauna. 



The shell is of considerable size, somewhat but not greatly oblique, 



