Fresh-Water Shells. 199 



very small, and the body -wliorl about seven tentlis the length of 

 the whole shell ; surface generally dead, and somewhat checked 

 with irregular revolving and longitudinal raised lines; aperture 

 large, usually three fifths the length of the shell, oval, broadly and 

 sub-equally rounded both behind and before ; the lip is consider- 

 ably everted in front, and along the left margin, where it is not 

 closely apprcssed to the whorl, and leaves a small, hut evident 

 umbilical opening ; callus rather abundant ; fold on the pillar 

 slight, and smoothly rounded. Length A inch, of aperture | inch, 

 breadth ^\ inch, divergence 45*^. 



This species is found in most regions, about the muddy margins 

 of ponds and pools. 



It is intermediate between L. eludes and L. modicellus. Its spire 

 is proportionally more slender, its suture deeper, its aperture pro- 

 portionally larger and more oval, the fold of its columella 

 much less conspicuous, and it is a much more fragile shell than 

 the former. The latter, while it has the large, oval aperture, the 

 deep suture and shouldered whorls, is still more fragile, of a deep 

 green-color, and is a short, inflated shell, with a much greater 

 divergence of the spire, and with one whorl more than L. desidiusa. 

 The habits of the two last are similar, but the animal of desidiusa 

 is a much lighter green, and has not the remarkable white dots 

 between the tentacula. 



The characters of the aperture and spire seem to be constant ; 

 that is, the aperture is always large and broadly rounded behind; 

 and the spire is tapering, the two whorls at the tip seeming some- 

 what as if superadded ? so that if a line should pass down one side 

 so as to touch all the whorls, this line would be concave. The 

 only variations I have noticed are, that the suture is sometimes 

 shallow, and the shoulder nearly wanting, so as to render the spire 

 more regularly tapering. Mr, Say's description is not definite, 

 and his figure is much shorter than the dimensions he ascribes to 

 it. He gives its length seven tenths of an inch, while it rarelv 

 exceeds half an inch. 



Limn.e'a Elodes. — (Say.) 

 ^ Shell tapering, elongated, turreted, thin and fra- 



gile, dull and dingy horn-colored, inelegant ; whorls 

 five, or a little more, the two smallest being gene- 

 rally broken oft"; they are regularly and largely 

 convex, not flattened or compressed posteriorly, but 

 the adjacent margins of two whorls curve regularly 

 to the deeply impressed suture ; the last whorl, 



