POMATIOPSIS. 295 



Limn is not an unaltered continuation of the lips as in that shell, 

 but is appressed to the surface of the penultimate whorl in the usual 

 manner of calcareous deposition upon that part (/SV///). 



Ranges from Lake kSuperior to Virginia. New Haven (^Linsleij^. 



Fig. 560 is drawn from an authentic specimen given by Mr. tSay 

 to the Philadelphia Academy. 



■ Oenus PO.IIATIOPSIS, Tryon. 18G2. 



Shell small, thin, smooth, long, sub-umbilicate. Spire turreted. 

 Aperture ovate, peritreme reflected. Operculum corneous. 



Pomatiopsis lapidaria. 



Shell turreted, sub-unibilicate ; whorls six, indistinctly wrinkled ; suture im- 

 pressed ; aperture long, ovate-orbicular. 



Cyclosloma lapidaria. Say, Journ. A. N. S. Phila. i. 13 (1817) ; Binxey's ed. 59. 

 Amnkola lapidaria, Haldeman, Mon. 18, pi. 1, fig. 10 (1844 ?) ; Journ. A. N. S. Phila. 



viii. 200 (1842). 

 Paladina lapidaria, Say, Nich. Encyc. 3d ed. (1819); Binney's cd. ."16. — Kuster, in 



Chemn. 2d cd .54, pi. 10, figs. 21, 22. — De Kay, N. Y. Moll. 86 (1843). 

 Mdania lapidaria, Lewis, Bost. Proc. viii. 2.").'i ; Phila. Pr. 1862, 290 (no descr.). 

 Pomatiopsis lapidaria, Tryon, Proc. Phila. Acad. 1862, 452 (no descr.). — W. G. Bix- 



ney, L. and Fr. W. Shells, iii. 93, figs. 186-188. 



Shell turreted, sub-umbilicate, with six volutions, which are obso- 

 Ictely wrinkled across ; suture impressed ; aperture longi- 

 tudinally ovate-orlucular, operculated, rather more than one % 

 third of the length of the shell. Length, about one fifth of nL 

 an inch. p. inpi- 



Collection of the Academy of Natural Sciences. 



Inhabitant not so long as the shell, pale ; head elongated into a 

 rostrum as long as the tcntacula, and emarginate at 

 tip ; tentacula two, filiform, acuminated at tip, short ; 

 eyes prominent, situated at the external or posterior 

 base of the tentacula ; base or foot of the animal di- 

 lated, oval, ol)tuse before and behind. 



Found under stones, <fcc., in moist situations, on the 

 margins of rivers. Like those of the genera Limncca 

 and Planorbis, this animal possesses the faculty of A'^imainfp. 

 crawling on the surface of the water in a reversed posi- Enili^ged^ 

 tion, the shell downward (Scri/'). 



This is a widely distributed species, ranging at least from Georgia 



