136 PALEONTOLOGY OF NEW- YORK. 



The interior of both valves is strongly pustulose, but the muscular markings 

 are not defined in the specimens examined. 



In many of the smaller specimens from the Corniferous limestone, there are 

 but from twelve to sixteen strong rounded strife, and the ventral valve is very 

 gibbous (figure 2, Plate 20). In some specimens the cardinal extemities arc con- 

 siderably produced, but this is not a common feature. The species is sometimes 

 associated with C. lineata and C. lepida in the same fragment of stone. In the 

 Hamilton group, it has been found more frequently in the harder semicalcareous 

 beds. 



The great variation in convexity, number of striae and general aspect, leads 

 me to suspect that the following (C dejlecta) may perhaps be only another phase 

 of the same species. 



Geological formation and localities. In the Corniferous limestone of Manchester, 

 Ontario county ; at Williamsvillo and Clarence-hollow ; and on the Indian 

 Reservatioh to the southeast of Buffalo in Erie County. These localities furnish 

 the gibbous forms with strong striae designated C. laticosta. In the Marcellus 

 shale, the species is found at Avon in Livingston county, at Crooked creek near 

 Darien in Genesee county, and at Alden in Erie county. It occurs in the Hamil- 

 ton group at Pratt's falls, and in other localities in Onondaga and Madison 

 counties. 



Chonetes deflecta. 



PLATE XXI. 



Chonetes deflecta : Hall in Tenth Report on Stat« Cabinet, p. 149. 1857. 

 Choneles gibbosa : Id. Ibid. p. 145. 1847. 



Shell semielliptical ; length and width as four to five or eight to nine, 

 but rarely proportionally wider. 



Ventral valve extremely gibbous, regularly arched, the greatest eleva- 

 tion being about the middle of the length ; abruptly depressed towards 

 the cardinal angles, which are flattened, with the extremities deflected 

 to the ventral side. The umbo is a little elevated above the cardinal 

 margin, and the minute apex (in perfect specimens) projects a Kttle 

 over the area. 



Dorsal valve deeply concave, but not equalling the convexity of the 

 ventral valve. 



Area of the ventral valve narrow, with the exterior margin declining in 

 a gentle curve to the extremities : the triangular foramen is partially 



