Raymond : Gastropoda of the Chazy Formation. 195 



Chazy Limestone has forced upon the writer the conviction that the 

 three species heretofore described are all founded on more or less im- 

 perfect specimens of the same type. 



The first to be described, Bellerophon sulcatinus Emmons, was, 

 according to the figure, a large specimen retaining the shell, and 

 showing the characteristic reticulate surface markings and the slit band. 

 Under Emmons' name for this species, Hall figured a characteristic 

 specimen which retained a part of the shell, and then, under the name 

 Bucania rotundata, he figured an exfoliated specimen of the same 

 species. This second species was distinguished from the preceding, 

 first, because it was more rotund ; second, the inner volutions were 

 less angular ; third, the surface was marked only by transverse striae or 

 lines of growth, with a few stronger wave-like lines ; and fourth, there 

 was no indication of a carina or of a depressed line along the back of 

 the shell. 



The first two statements are not upheld either by Hall's figures or 

 by the types. The third and fourth characters mentioned can be 

 seen on specimens of Bucania sulcatina from which the outer shell 

 has been either partially or entirely split off. When partially exfoli- 

 ated the shell shows transverse lines parallel to the margin of the lip. 

 (See figure 15, Plate XLIX.) 



Bucania champlainensis was described from shells from the upper 

 part of the Chazy formation at Valcour Island. The ordinary speci- 

 mens in that horizon do not show the surface characters well, as they 

 usually occur in a limy clay that adheres too closely to be removed 

 without destroying fine detail. A few specimens were, however, ob- 

 tained from a purer layer which lies directly upon the one from which 

 Whitfield's specimens were obtained, and these show exactly the same 

 surface markings as Bucania sulcatina. Whitfield distinguished the 

 species Bucania champlainensis from Bucania rotundata as having 

 more rounded volutions and a very small umbilicus, but an examina- 

 tion of a series of sections shows that both the form of the umbilicus 

 and the angularity of the volutions depends upon the plane of the sec- 

 tion and the amount of distortion of the specimens. Therefore, this 

 distinction cannot be relied upon to distinguish species. It would 

 seem then that all these large Bucanias must be united under the one 

 species, Bucania sulcatina (Emmons), which is the type of Hall's 

 genus, Bucania. 



This species is especially common at two horizons. One is in the 



