142 THE NAUTILUS. 



Somatogyrus pilsbryanus n. sp. PI. v, figs. 20 and 21. 



Shell small, gibbous-globose, scarcely perforate, rather thin, light 

 yellow-horn colored, smooth, lines of growth very fine. Spire short, 

 conic, obtuse. Whorls 3^, those of the spire convex, separated by a 

 well-impressed suture, body whorl large, very convex, gibbous. 

 Aperture large, widely ovate, obtusely angled above and regularly 

 rounded below. Umbilical region impressed. Umbilicus a mere 

 chink. Columella concave, with a heavy, flat callus, which becomes 

 thin and transparent on the parietal wall. Alt. 3, diam. 3 mm. 



Tallapoosa river, Tallassee, Ala. 



This is another of the new species discovered by Mr. Hinkley. It 

 occurred quite abundantly and is a well marked and distinct form. 

 It is related to S. parvuhis, Tryon (PI. v, figs. 22 and 23), in gen- 

 eral appearance, but differs in the wide, gibbous body whorl, more 

 obtuse apex and in the heavy, flat, columellar callus, S. parvuhis 

 being more acutely conical, with the body whorl regularly rounded 

 and with a narrow, rounded, columellar callus. Dr. Pilsbry has 

 kindly compared it with the types of Tryon's species and concurs in 

 its specific distinctness. I take great pleasure in naming it after him. 



A NEW SUBSPECIES OF POLYGYRA TEIDENTATA. 



BY H. A. PILSBRY. 



Polygyra tridentata discoidea n. subsp. 



The shell is larger than tridentata^ more depressed, the spire 

 usually nearly flat. Whorls 5^, closely and sharply striate. Umbili- 

 cus more widely expanding at its opening, showing more of the pre- 

 ceding whorl. The aperture is more or less " dished," the parietal 

 tooth directed towards the upper lip-tooth, which while varying 

 somewhat in shape has a tendency to be rather wide and flat-topped. 

 The lower lip-tooth is more acute, both being strictly marginal. 



Alt. 9^, diam. 201 mm . 



Alt. 8, diam. 19 mm. 



Alt. 8-5, diam. 18^ mm. 



Charleston Landing, Clarke Co., Southern Indiana. Cotypes in 

 coll. A. N. S. P. and of L. E. Daniels. 



During a recent visit, Mr. G. H. Clapp called my attention to the 

 form of P. tridentata found around Cincinnati, and widely known in 



