LIMNJIA. 477 



somewhat chalky, and the brown, sub-marginal callus of the outer 

 lip is thus covered over. 



Tlie most common species found in Massachusetts, and one which 

 it is exceedingly difficult to describe, or to determine if it has been 

 already described. After much observation, and a comparison of 

 many individuals collected from various localities, and an exchange 

 of specimens with the most distinguished conchologists of this coun- 

 try, I have come to the conclusion that it must be regarded as the 

 L, elodes of Say. Its European analogue is L. paluslris. The only 

 Massachusetts shell which bears much affinity to it is L. dcsidiosa, 

 which is smaller, has a more slender spire, and larger aperture, 

 proportionally. But it is closely related to L. umhrosa and L. rc- 

 Jiexa of the Western and Middle States. Tlie former is more solid, 

 more corpulent, with the whorls and aperture more oblicpie, and its 

 color darker than that of our shell. The latter has the whorls still 

 more oblique, much less convex, forming a much less turreted and 

 regularly tapering spire ; the fold of the pillar much less prominent, 

 and the color yellowish. After all, these species are so nearly al- 

 lied, that no description, and perhaps no figure, will enable a person 

 to determine any one of them by itself. They must be learned by 

 comparison, and by interchanging specimens. But the difficulty does 

 not end here. It is no easy matter to assign the limits of the spe- 

 cies. No one presents a greater variety. The length of mature 

 shells varies from half an inch to an inch ; and it is remarkable 

 that the largest specimens are usually the most fragile. The sur- 

 face usually has an uneven, unfinished, inelegant aspect, coated 

 with mud ; but occasionally we find the conformation of the shell 

 perfectly regular, the color a shining, greenish horn color, and the 

 surface smooth and beautifully reticulated with longitudinal and 

 revolving lines. It is then a very pretty, fragile shell. Tlie aper- 

 ture is small in proportion to the shell, generally rather contracted ; 

 again, we find the lip beginning to expand, and in some specimens 

 received from Vermont, which I suppose to belong to this species, 

 the lip is broadly flaring. Young specimens might be confounded 

 with L. umbilicata, L. dcsidiosa, L. modicellus, and L. caperata; 

 but a little attention to the umbilicus, the aperture, the color, and 

 the revolving lines will enable us to distinguish them respectively. 

 The umbilicus is usually entirely obstructed by the overlaying cal- 

 lus ; but in some specimens it is partially open. 



[In my " Land and Fresh-Water Shells of North America," Part 

 II. p. 44, I have referred this species to L. pahistris, Miiller. — W. 

 G. B.] 



