KOTE ON THE GENERA BELLEROPHON, BUCANIA, CARINAROPSIS, 



AND CYRTOLITES. 



( See Vol. I, Pal. N. York.) 



PiCTET, in his very valuable work " Traite de Paleontologie,^^ 

 has united, under the Genus Bellerophon (Montfort), the typical 

 form of that genus, together with Bucania, Carinaropsis and 

 Cyrtglites. It is true that the principal distinctive feature of 

 the Bucania is the open umbilicus, showing the volutions together 

 w4th an exterior carina along the dorsal line, corresponding to a 

 channel on the inner side ; and the lip terminating in a deep* 

 sinuosity, and usually abruptly expanded ; while the lateral and 

 posterior parts of the lip are often much thickened, as is shown 

 in nearly all the» good specimens of B. troosti of D'Orbigny, a 

 lower Silurian form from Tennessee. Since this type is well 

 known, I shall not at present contend for the generic distinction, 

 believing that it will ultimately be found a useful designation. 



The Genus Carinoropsis was founded upon the external char- 

 acters, presented by a few specimens. These are, the usually 

 attenuated spire, the abruptly expanding body volution, and 

 shallow cavity, giving the shell a patelloid aspect. To this may 

 be added the character (perhaps not constant) of an attenuated 

 carina upon the dorsum. The shells are usually thin. 



The interior of the established species has not been deter- 

 mined, and I do not know whether or not they present differences 

 from the ordinary Bellerophon. 



Among some collections presented to me some time since by 

 Prof. Safford, State Geologist of Tennessee, and many others 

 more recently received (Oct. 1860) from Mr. S. S. Lyon of Jeffer- 

 sonville, Indiana, are several specimens having the form and exte- 

 rior character of those specimens referred to Carinaropsis. The 

 outer or body whorl beyond the columella for nearly half a volu- 

 tion is extremely expanded, the first volutions contracted and 

 forming a very inconsiderable proportion of the whole. In these 

 specimens the cavity presents a kind of septum as in Ceepi- 



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