94 PALEONTOLOGY OF NEW YORK. 



BELLEROPHON, Montfort. 



SPECIE8 OF THE UPPER HELDERBERG GROUP. 

 Belleropuon CURVILINEATUS. 



PLATE XXII, FIGS. 1-6. 



Bellerophon curpilineatut, Conrad. Jour. Acad. Nat. Sci. Phil., vol. 8, p. 269, pi. 16, f. 7. 1842. 

 " " " Hall : Descriptions of New Species of Fossils, etc., p. 27. 1861. 



•' " " Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 5.".. pi. 6. figs. 8, 9. 1862. 



" " " " IllustrationsofDevonian Fossils: Gasteropoda, pi. 25, tigs. 25-30. '76. 



Shell discoidal. Volutions four or five, compressed and sharply carinated on 

 the back, each one embracing about half the width of the preceding one, 

 the last scarcely more ventricose than the preceding, and bending almost 

 rectangularly at the umbilical edge. Aperture triangular, acute at the 

 anterior margin, which is deeply sinuate ; the curvature of the peristome 

 from the umbilical side receding about one quarter of a volution to the 



i 



dorsal line. The inner margins of all the volutions are exposed in the 

 cavity of the umbilicus. 

 Surface marked by fine striae of growth, which follow the curvature of the 

 peristome, making a retral curve of about one quarter of a volution ; 

 often slightly fasciculate, but sometimes the striae are in regular fascicles 

 of about six or seven finer ones, with a fine sharply elevated one separating 

 them. The dorsum is sharply carinate. 



The casts are angular on the back, showing a wide umbilicus, revealing the 



inner volutions. This species has somewhat the form and proportions of the 



B. dubia of d'Orbigny; but the umbilicus is proportionally larger, and the 



outer volution less rapidly widening towards the aperture. The following is 



the author's description of B. curvilineatus : 



" Discoid ; volutions exposed ; back sharply carinate ; surface with oblique 

 arched striae." 



Tbis species, cited by Mr. Conrad as occurring in the Onondaga limestone, is 



more abundant in the Schoharie grit ; though in this rock it rarely preserves the 



shell. In size, the specimens of this species vary from about one quarter of an 



