roMATiopsis. 295 



biura is not an nnaltcrcd continnation 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 (>Sa//). 



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



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

 to the Philadelphia Academy. 



Genus POilIATIOPSIS, Tryon. 1SG2. 



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

 Aperture ovate, peritreme reflected. Operculum corneous. 



Pomatiopsis lapidaria. 



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

 pressed ; aperture long, ovate-orbicular. 



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

 Amnicola lapidaria, Haldeman, Men. 18, pi. 1, fig. 10 (1844 ?] ; Journ. A. N. S. Phila. 



viii. 200 (1842). 

 Paladina lapidaria. Say, Nich. Encyc. 3d ed. (1819); Binney's ed. 56. — KiJSTER, in 



Che.m.v. 2d ed .54, pi. 10, figs. 21, 22. — De Kay, N. Y. Moll. 86 (1843). 

 Mtlania lapidaria, Lewis, Best. Proc. viii. 255 ; Phila. Pr. 1862, 290 (no descr.). 

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



NEY, L. and Pr. W. Shells, iii. 93, figs. 186-188. 



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

 letely wrinkled across ; suture impressed ; aperture longi- 

 tudinally ovate-orbicular, operculated, rather more than one a 

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

 an inch. p. lapi- 



Collection of the Academy of Natural Sciences. 



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

 rostrum as long as the tentacula, 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, obtuse before and behind. 



Found under stones, &c., in moist situations, on the 

 margins of rivers. Like those of the genera Limncsa 

 and Planorbis, this animal possesses the faculty of AnimaiofP. 

 crawling on the surface of the water in a reversed posi- Enlarged. 

 tion, the shell downward (/Sa/y). 



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



