94 NEW YORK STATE MUSEUM 



Clitambonites americanus (Whitfield) 



PI. 4, fig. 14-19 



The Snake Hill beds furnished several specimens of a Clitambo- 

 nites that in general aspect resembles Clitambonites 

 di versus (Shaler). Since in the Ohio basin, however, several 

 similar species have been distinguished, we have sent our specimens 

 to Dr August F. Foerste of the Kentucky Geological Survey, who 

 has kindly given us the following brief sketch of the Kentucky 

 species : 



In Kentucky, we have three species of Clitambonites. The lowest 

 of these occurs in the Perryville bed. This is characterized chiefly 

 by the great number of rather fine radiating striations ; and the 

 relatively greater width of the shell, compared with Clitam- 

 bonites diversus. In your specimens the striations are 

 coarser than in these Kentucky specimens, and the shell is narrower. 



The second horizon occurs in the upper part of the Winchester, 

 Cynthiana, or Catheys horizon (various names for the same set of 

 strata). This species is not well understood. It contains radiating 

 striae about as coarse as yours, but apparently is a smaller, shorter, 

 broader species. 



The third horizon is at the base of the Eden, in what I have called 

 the Rogers Gap division of the Eden. To this species I have given 

 the name Clitambonites diversus-rogersensis 

 (title 64, page 323). As far as the coarseness of the radiating striae 

 is concerned, it appears to be about the same as in your specimens. 

 The width of the Kentucky specimens, however, is greater. This is 

 strikingly shown in the case of the brachial valves, in which the 

 ratio of length to width often is as 15 or 16 to 25. In your speci- 

 men the dimensions are as 17 to 21. 



To me your specimens most resemble Clitambonites 

 americanus Whitfield, an earlier form than any found in 

 Kentucky. In fact, I do not know in what respect your specimens 

 differ from that species. 



Of course, you are familiar with Clitambonites diver- 

 sus. This is one of the larger species, similar to Clitam- 

 bonites americanus, but with the shell much more 

 strongly convex from beak to anterior margin. Concentric striae 

 are much more constant and conspicuous. The bombiform con- 

 vexity of the pedicel valve as a rule attracts instant attention. In 

 those specimens of Clitambonites arnericanus, which 

 I have seen, the antero-posterior curvature is more like that in your 

 specimen. 



Clitambonites americanus (Whitfield) was originally 

 described and figured as Hemipronites americanus 

 (title II, page 243), but referred by Winchell and Schuchert (title 



