110 PALJEOiVTOLOGY 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 B. 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 strife 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, FIGS. 2-16. 
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-fourth Rep. N. Y. State Mus. Nat. Hist., p. 200. 1S72. 
“ “ “ Twenty-seventh Rep. N. Y. State Mus. Nat. Hist., pi. 13, fig-. 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. 
