POMATIOPSIS. 295 



bium 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 ((S«7/). 



Ranges from Lake Superior to Virginia. New Haven {Liiislejj^. 



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

 to the Philadelphia Academy. 



Oenus POITIATIOPSIS, Tryon. 1SG2. 



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

 Aperture ovate, peritreme reflected. Operculum corneous. 



Pomatiopsis lapidaria. 



Shell turreted, suh-umljilicate ; whorls six, indistinctl}^ wrinkled; suture im- 

 pressed ; aperture long, ovate-orbicular. 



Cyclosloma lapidaria. Say, Journ. A. N. S. Thila. i. 13 (1817) ; Bixney's cd. 59. 

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



viii. 200 (1842). 

 Paludina lapidaria. Say, Nicli. Encyc. 3(1 cd. (1819); Binney's cd. ."ie. — KuSTER, in 



CuEMN. 2a ed .54, pi. 10, figs. 21, 22. — I)e Kay, N. Y. Moll. 86 (1843). 

 MAania lapidaria, Lewis, Best. Proc. viii. 2.-).5 ; Phila. Pr. 1802, 290 (no dcscr.). 

 Pomatiopsis lapidaria, Tryo\, Proc. Phihi. Acad. 1862, 452 (no dcscr.).— \V. G. Bix- 



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



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

 letely wrinkled across ; suture impressed ; aperture loiigi- 

 tudiiially ovatc-orl)icular, operculated, rather more than one a 

 third of the length of the shell. Length, about one fifth of (A 

 an inch. p. lapi- 



Collection of the Academy of Natural Sciences. 



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

 rostrum as long as the tcntacula, and emarginatc at 

 tip ; tentacula two, filiform, acuminated at tip, short ; '°' '^'" 



eyes prominent, situated at the external or ]>osterior 

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

 lated, oval, obtuse before and beliind. 



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

 margins of rivers. Like those of the genera Limncea 

 and P/anorbis, this animal possesses the faculty of 

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

 tion, the shell downward (Sai/^. 



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



