so FIFTEENTH REPORT ON THE CABINET OF NAT» HISTORY. 



ORTHOCEKAS PERELEGANS? 



Compare Orthoceras perelegans : Salter, Memoirs of the Geol. Survey of Great 

 Britain, Vol. ii, part i, pag. 354, pi. 13, f. 2, 3, 4. 



Shell cylindrical, gradually tapering : sipliuncle central. 

 Surface undulated by rounded, subundulating or slightly oblique 



ridges, and marked by fine strise of growth which are essentially 



parallel to the annulations; without longitudinal strise. 



I have seen but a single fragment of this species, from the Hamilton 

 group : it differs conspicuously from the preceding species, in the absence 

 of longitudinal striae, and usually in the more numerous annulations in the 

 same space. Without more specimens, I have not the means of finding any 

 specific difference between this and the species of Mr. Salter. 



Geological formation and locality. In the coarse shales of the Hamilton 

 group : near Hamilton, Madison county, N.Y 



ORTHOCERAS ^GEA(n.s.). 

 Shell cylindrical, gradually tapering : septa distant, very convex; 



siphuncle central? 

 Surface undulated by broad undefined annulations, crossed by 



prominent longitudinal rounded strise, which are distant from 



each other, with a fainter one between. Transverse strise obscure 



in the specimen examined. 



This species differs from O. profundum of the Upper Helderberg lime- 

 stone, in its surface-markings, in the rounded character of the longitudinal 

 strise, and in the presence of the intermediate finer strise : the broad un- 

 defined annulations are also a marked feature, though this may not be 

 constant in all parts of the shell. 



Geological formation and locality. In the calcareous beds of the Ha- 

 milton group in Madison county, N.Y. 



[ September, 



