672 



NORTH AMERICAN INDEX FOSSILS. 



Minute (1.5 mm. in height and width) with three or four rapidly 

 expanding whorls, last one ventricose ; aperture subcircular, outer 

 lip thin, inner lip slightly reflexed, scarcely covering umbilicus. 



Abundant in Portage (Naples) beds throughout western New 

 York, etc. Pelagic. (Clarke refers them to the pteropods. They 

 may be pelagic protoconch stage of other gastropods.) 



LXVI. Pycnomphalus Lindstrom. 

 Round-whorled, strongly embracing shells, with the umbilicus 

 covered by an inner flange-like expansion of the shell, which thus 

 appears non-umbilicate. In the internal mold a large umbilicus is 

 seen. Siluric. 

 209. P. solarioides (Hall). (Fig. 931.) Siluric. 



FlG. 931. Pycnomphalus solarioides. a, apical view of internal mold; b, lateral 

 views of same ; c, vertical section, showing prominent inner spiral lamella ; d, umbil- 

 ical views of shell. (After Whiteaves, Pal. Fossils, III.) 



Large, rather low-spired whorls strongly embracing, viewed from 

 above, very gradually enlarging, and numerous. Base broad, 

 flat, without umbilicus in shell. 



Guelph of Canada, New York, Ohio (?). 



