132 



NORTH AMERICAN INDEX FOSSILS. 



generally large, internal; gerontic aperture strongly contracted 

 laterally, leaving a long, hyponomic area. Siluric. 



189. P. nestor Hall. (Figs. 1380, 1381.) Siluric. 

 Of moderate size, and ovoid section; living chamber ventricose, 



nearly as high as long ; aperture laterally contracted to long narrow 

 slit, which widens to broad aperture ventrally, and a smaller one 

 dorsally, without pronounced prolongation; siphuncle submarginal, 

 Niagaran of Wisconsin. 



190. P. parvum Hall and Whitfield. (Fig. 1382.) Siluric. 



Fig. 1382. Phragmoceras par- 

 vum. (Pal. Ohio. ) 



Fig. 1383. Phragmoceras angusium, X 

 i. ( After Kindle, 28th Ind.) 



Small, strongly curved, rapidly expanding, transversely broadly 

 ovate below, but more flattened above; hyponomic slit prolonged 

 ventrally into a tube-like projection; siphuncle minute. 



Guelph of Ontario, New York and Ohio; Niagaran of northern 

 Indiana. 



191. P. angustum Newell. (Fig. 1383.) Siluric. 



Large, strongly curved, moderately compressed, less rapidly 

 expanding than either of preceding; sutures sinuous, with broad 

 lateral lobe. 



Niagaran of northern Indiana. 



