HO PALJEOSTOLOQ Y OF NEW YORK. 



Surface marked by fine, closely arranged concentric striae of growth which are 

 abruptly incurved towards the dorsum. The dorsum is elevated in a 

 rounded, not carinate, band, which is distinctly limited at the margins, 

 and upon which the striae are rather gently arched. 



This species is essentially different from any others here described except 

 the B. natator ; and from the typical form of this it is certainly distinct. It 

 has the general aspect of jB. patulus, but differs by the absence of the strong 

 concentric ridges upon the summit of the outer volution, and especially by 

 the presence of a dorsal band. It also resembles B. triliratus in form, but 

 is not marked by the central and lateral ridges, nor has it any evidence of 

 radiating or revolving striae so characteristic of that species. 



Formation and locality. The specimen has been placed in my hands as 

 coming from the Chemung group, but from the character of the rock and 

 certain associations I infer that it has been derived from the coarser shales of 

 the Hamilton group in some one of the eastern counties of the State. 



Bellerophon Leda. 



PLATE XXIII, KIGS. J-16. 



Bellerophon. Leda. Hall. Descriptions of New Species of Fossils, etc., p. 30. 1861. 



" " Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 58. 1862. 



" " " H. & W. Twenty-fojrth Rep. N. Y. State Mus. Nat. Hist., p. 200. 1872. 



" " " Twenty-seventh Rep. N. Y. State Mus. Nat. Hist., pi. 13, &g. 1. 1875. 



" " " Illustrations of Devonian Fossils : Gasteropoda, pi. 24. 1876. 



Shell subglobose, often a little flattened upon the dorsum ; body-whorl ventri- 

 . cose, very rapidly expanding. Aperture very wide: peristome abruptly 

 spreading, broadly sinuate in front and sometimes with a deeper notch in 

 the middle, the margin gently recurved, joining the volution a little on the 

 ventral side, where it is thickened, somewhat abruptly curving over and 

 partially enclosing the small umbilicus, and extending in a callus over the 

 columellar lip, which is sometimes distinctly striato-pustulose. 



