1906.] 



NATURAL SCIENCES OF PHILADELPHIA. 



565 



moderately elevated, the apex depressed, radially striate, situated 

 behind the posterior third, and much nearer the right than the left 

 margin. Surface densely and minutely striate concentrically, and 

 showing faint traces of radial striae. Anterior and left slopes convex; 

 right and posterior slopes concave. Length 4.3, width 2.75, alt. 1.4 mm. 



Fig. .5. — Ancylus walkeri. 



Arkansas: Rogers, Benton Co., on fallen leaves in a fish pond, 

 Ferriss and Pilsbry, 1903. Types No. 87,479, A. N. S. P. 



This Ferrissia has nearly as excentric an apex as A. excentricus, 

 decidedly more so than in A. rivularis or tardus. The summit of the 

 shell is in front of the somewhat depressed apex. It is named for Mr. 

 Bryant Walker, who has published an excellent revision of the Eastern 

 Ancyli. 



PHYSID^. 

 Physa Integra Hald. 



Rogers, Benton Co. , Ark. A brown form of the species. 

 Physa albofilata Anc. 



Chadwick, Christian Co., Mo.; abundant and the only Physa found. 

 In small rivulets it is dwarfed. 



Physa rhomboidea Crandall. 



Nautilus, XV, p. 44, pi. 2, figs. 6, 7, August, 1901. * 



Cf. A. Springer, Proc. A. N. S. Phila., 1902, p. .514, pi. XXVI. 



The shells we took from the stream running through Limestone Gap, 

 I. T., asree with this form received from Mr. Crandall. 



POMATIOPSIDiE. 

 Pomatiopsis lapidaria (Say). 

 Rogers, Benton Co., Ark. 



