504 FAUNA CANADENSIS. 



strongly pronounced carinse on the whorls. It is thus rendered a 



matter of opinion whether the two species should not properly be 



thrown into one. 



JJab. — Common, adhering to water plants, in depths of from one 



to five fathoms. 



23. Paludina decisa, Say. 



Shell ovate, with an elongate spire. Whorls four or five, rounded, 

 with faintly-marked or obsolete transverse striae. Aperture sub- 

 ovate, angulated posteriorly ; lip thin. Operculum horny, concentri- 

 cally striated. 



Colour variable, generally olive-green, often tinged orange-brown 

 or russet ; interior generally of a purplish tint. 



Length of large specimens one inch, by seven-tenths of an inch in 

 diameter ; of small specimens three-tenths of an inch by one-fifth of 

 an inch in diameter. 



llab. — In a living state and in all stages of growth, in from two to 

 three fathoms, on a sandy bottom. 



24. Amnicola porata, Say, sp. 



Shell minute, obtusely conical, of four rounded whorls, which are 

 separated by a well-marked suture, and have a smooth sixrface. 

 Aperture somewhat ovate, and slightly angulated posteriorly, the 

 posterior half of the inner lip confluent with the columella. Umb- 

 ilicus small but well-marked. Colour olive-green. Dimensions of 

 adult shell nearly two-tenths of an inch in. length by a little more 

 than one-tenth of an inch in diameter. 



Our specimens differ in some trivial respects from typical examples 

 of Amnicola (Paludina) 2^orata, Say ; but these difierences do not 

 appear to have more than a varietal value. 



Hah. — Yery abundant, crawlmg over the stems of Chara and 

 Anacharis, in from one to three fathoms. 



25. Limnma jugularis, Say. 



Shell of large size, thin, nearly translucent, with ventricose whorls- 

 Whorls six in number, rounded. S]3ire regularly tapering, a little 

 shorter than the aperture. Aperture large, the inner lip nearly 

 straip-ht, with a deep, oblique columellar fold. Outer lip somewhat 

 expanded. No umbilicus. Colour olive, light brown, or ferruginous. 

 Length of largest specimen observed, one inch and a half, with a 

 diameter of seven-tenths of an inch. 



Ilab. — Abundant in shallow water at the " Island." 



