j 06 PALEONTOLOGY OF NEW YORK. 



specimens observed are more or less distorted by pressure, and tbe surface- 

 markings are but partially preserved. 



Formation and localities. In shales of the Hamilton group, at York, Livingston 

 county, and at Pratt's Falls in Madison county, N. Y. 



BelLEROPHON ACUTILIRA. 



PLATE XXV, FIGS. 4-8.« 



BtUemphon acuiilira. Hall. Descriptions of New Species of Fossils, etc., p. 28. 1861. 

 " Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 56. 1862. 



" " " Illustrations of Devonian Fossils : Gasteropoda, pi. 25. 1876. 



Shell ovoid or subglobose ; the inner volutions discoid, and exposed in the 

 rather large umbilicus; the body- volution becoming ventricose and much 

 expanded towards the aperture; the ventro-lateral margin angular, and 

 sometimes almost carinate from the rectangular bending into the umbilical 

 depression ; dorsum obtusely subangular, not carinate ; aperture suborbic- 

 ular, a little wider than high ; peristome deeply sinuate in front, and the 

 posterior margin slightly modified by the preceding volution. 



Surface marked by regular, subequidistant, fine stria?, which bending forward 

 from the ventral edge of the volution, make a broad curve on the side, 

 and turn abruptly backward, making a sharp bend on the dorsal line. 

 The dorsum is angular on the upper part of the last volution, but becomes 

 regularly convex, with a less abrupt curvature of the striae, upon the more 

 expanded part toward the aperture. 



In one specimen of this shell, I find characters corresponding to those given 

 by Mr. Conrad to B. brevilineatus. The striae proceeding from the umbilicus 

 are well marked at first, become obsolete on the side of the volution, and are 

 again well marked on the dorsum. This character obtains only on the last 

 half of the outer volution; above this the striae are uniform over the whole 

 surface. The periphery is obtusely angular, and it does not appear, therefore, 

 that this can be identical with the species of Mr. Conrad. At certain stages 



— , , , . : __ 



* Fig*. 6, 7 and 8 were erroneously referred in the Illustration* of Devonian Fossils (figs. 19, 20, 21) to 

 CyrtolUa niUUa. 



