The Pond Snails 



fight, to see them twist and twirl, performing such quick and 

 curious evolutions while seemingly floating in mid-water, is 

 astonishing, even to the patient student of Nature's wonders. 



Dr. Jeffreys says that all snails clean each others' shells of 

 confervae, the passive individual remaining patiently quiet while 

 the "operator" goes over the entire surface with its rasping 

 tongue. 



P. hypnorum, Linn,, described as a gymnast above, is the 

 most rapid of all aquatic snails. It cleans its own shell to the 

 very apex. European species found also in America. 



The Tadpole Pouch Snail (P. gyrina, Say) is an inch long, 

 the last of the six whorls very large, the oval aperture nearly 

 two-thirds the length of the shell. The lip is slightly thickened 

 within, the columella overlaid with a callus. 



Habitat. — Vermont and Georgia, westward. 



The Jug Physa (P. ampullacea, Gld.) is a shining, delicate, 

 much swollen species, its lip tinged with red. The aperture 

 is wide and about five-sixths the total length of the shell. The 

 columella is deeply excavated anteriorly. Length, i inch. 



Habitat. — Oregon, Washington. 



P. ancillaria, Say, has a dainty, flesh-tinted, translucent 

 shell with an inflated body whorl, and an oval aperture a trifle 

 shorter than the shell. Both lips are slightly thickened with a 

 white callus. The apex is blunt and dark. 



This species is numerous on piers of wharves in eastern 

 rivers, going up and down with the turns of the tide. It also 

 burrows in mud as soon as the water goes off, reappearing as the 

 water rises. Length, h inch. 



Habitat. — New England to Louisiana. 



The Small-mouthed Physa (P. microstoma, Hald.), is a 

 brownish yellow, elliptical, solid shell, with aperture contracted, 

 lip thickened, and columella bearing two pearly teeth. Length, 

 § inch. 



Habitat. — Kentucky, Ohio. 



THE ORB SNAILS. TRUMPET SNAILS 



Genus PLANORBIS, Guettard 



Shell a flattened, bi-concave, dextral coil, spire depressed; 

 aperture small, rounded; margin simple, upper margin produced. 



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