1 1 g PA LAVONTOLOG 7 OF NEW YORK. 



nearly the form of the European B. trilobatus, but with very different surface 

 characters. 



Formation and locality. From the shales of the Hamilton group at Norton's 

 Landing, Cayuga lake, N. Y. 



Bellerophon crenistria. 



TLATE XXV, FIGS. 16-18. 

 Bellerophon crenixtria. Hall. Illustrations of Devonian Fossils : Gasteropoda, pi. 25. 1876. 



Shell ovoid. Inner volutions small and gradually enlarging, partially exposed 

 in the umbilicus ; outer volution ventricose, somewhat rapidly and 

 regularly expanding to near the aperture, where it is more abruptly 

 spreading ; rather broadly and abruptly sinuate in front ; flattened or 

 slightly concave on the dorsum, the flattened portion distinctly limited, 

 and the margins often subcarinated by stronger longitudinal striae. On 

 each side of these limits the shell is usually more or less depressed, giving 

 a subtrilobate aspect to the body-volution. 



Surface marked by distinct revolving stria? which are regularly crenulated, 

 producing a papillose aspect ; the crenulations are arranged parallel to the 

 lines of growth, curving forward from the umbilicus, and thence gently 

 backward over the periphery ; these lines are usually distinctly arched 

 upon the flattened or concave dorsum. 



This species is so conspicuously different from every other one in the forma- 

 tion under consideration that there are no features for comparison. The gen- 

 eral aspect of the outer volution is subtrilobate, with the margins somewhat 

 spreading and the front sinuate. The dorsal band is limited on each side by 

 stronger single, or sometimes duplicate revolving stria?, presenting a slightly 

 different aspect in the crenulations which are more oblique ; two or three 

 of the central striae are sometimes apparently quite independent of the others 

 in the arrangement of the crenulations. In different individuals the revolving 

 >tri:e exhibit considerable variation ; in some they are continuous with slightly 

 nodulose elevations, and in others, distinctly pustulose — the prevailing character 



