THE NAUTILUS. 



105 



Duchess Co., New York (W. S. Teator); Post Pliocene at White 

 Pond, New Jersey (Dr Joseph Leidy); and Saginaw Bay, 

 Michigan (Prof. M. Miles.) 



Differs from V. t. xi/n/i/c.r, Old by having a basal carina and 

 from F. t. confusa Wkr. by lacking a keel at the shoulder. 



VALVATA TRICARINATA BASALIS n. var. figs. 3, 4. 



Shell discoidal, thin, translucent, greyish corneous, spire 

 truncate, slightly elevated, apex impressed, suture linear, shal- 

 low. Whorls 3^, the first ones with a median carina, body- 

 whorl slightly descending at the aperture, with two strong 

 carina?, the upper surface between the suture and the shoulder 

 keel flat, slightly convex between this and the peripheral ca- 

 rina, base evenly rounded to the rather large deep umbilicus, 

 surface rather dull, sculptured with irregular growth striee. 

 Aperture irregularly truncate orbicular, lip thin, angular at 

 the suture, upper carina and peripheral keel ; base and colum- 

 ella evenly arcuate, upper lip straight. 



Alt. 2.56 diarn. 4.15, apert. alt. 1.69, diam. 1.74 mm. 



Type in the collection of the Academy of Natural Sciences 

 number 11995 from the Hudson River, New York (W. M. 

 Gabb). Also in the collection from Vermont (J. S. Phillips). 



Differs from V. tric.arinata Say by lacking the basal carina, 

 and from V. t. confusa Wkr. by the absence of a basal keel and 

 in having a peripheral carina. 



