Raymond : Gastropoda of the Chazy Formation. 209 



Description. 



Shell small, with about four rather flat-sided whorls which expand 

 gradually. Apical whorl smooth, while the succeeding whorls bear 

 four to six revolving ridges. Sutures deeply impressed, the side of 

 the previous whorl meeting the top of the next whorl at a right angle. 

 The lower surface of the body whorl is gently convex ; the umbilicus 

 is closed. In addition to the sharp revolving keels, the surface is 

 marked by fine, nearly vertical lines, between which are somewhat 

 deep depressions which do not cross the revolving keels, thus giving 

 the shell a somewhat cancellated appearance. 



Locality. — This shell is found near the Normal School at Pitts- 

 burgh, New York, and on Valcour Island. The holotype is in 

 the New York State Museum. The plesiotypes are in the Yale 

 Museum. 



Gyronema leptonotum Raymond. 



(Plate LV, figure 15.) 



Eunema leptonotum Raymond, 1905, American Journal of Science, 

 Series 4, Vol. XX, p. 378. 



Description 



Shell small, with about four whorls which expand gradually toward 

 the base. The whorls are all convex, the sutures deeply impressed. 

 The first three whorls are smooth and Holopea -like. The fourth, or 

 body whorl, is ornamented by five sharp revolving ridges, equally 

 spaced. These ridges are crossed by fine vertical lines which are 

 close together and give the ridges a flattened appearance. The 

 aperture is not seen. The height of the shell is 5 millimeters ; the 

 width at the body whorl 3.5 millimeters. 



It is evident that this species is closely allied to Gyronenia historicinn 

 Hudson, but may be readily distinguished from that shell by its some- 

 what slenderer form and the presence of two or three smooth apical 

 whorls instead of one. 



This shell is not uncommon in the Chazy, but on account of its 

 small size and liability to exfoliation it is often overlooked, or is in 

 too imperfect a condition to be positively indentified. 



Locality. — Lower Chazy at Chazy, New York. 



The type is in the Yale Museum. 



