472 LIMNiEID^. 



left margin the edge is slightly turned over a minute umbilicus, and 

 forms a considerable fold ; a tliin, closely adhering enamel stretches 

 across from it to the angle of the aperture ; the inner lip is so 

 arched as to display a considerable portion of the interior of the 

 shell. Length, eight tenths of an inch ; breadth, five tenths of an 

 inch; divergence, sixty-eight degrees. Of another specimen, length, 

 thirteen twentieths of an incli ; breadth, four tenths of an inch ; 

 divergence, fifty-six degrees. 



Inhabits stagnant pools and miry places, and is common. It is 

 found at maturity very early in the spring. 



The species has been found from Canada and Nova Scotia and 

 Lake Superior to Georgia. Its wide range and variable form has 

 caused its being described under several names. 



The animal is large, semi-transparent, of a dusky or light drab 

 color, dotted with silvery white. It is very sluggish in its motions. 

 The head above is slightly tinted with lilac. 



This very brittle shell has rather the aspect of Succinea than of 

 Limncca. It varies a good deal in form, being in some specimens 

 rather slender, and in others broad aud distended. The aperture 

 is usually somewdiat dilated, especially at its broadly-rounded base ; 

 but occasionally the outer lip is pressed inwards. The surface is 

 shining, and delicately corrugated by revolving lines. 



Var. CHALYBEA. 



Fig. 145. 



The spire is more pointed, its divergence being only fifty degrees ; 

 the aperture is more expanded, and the fold on the inner lip more 

 obvious. It is thin, but not very brittle, ringing like hard-burnt 

 crockery. The last whorl is partially detaclied from the preceding 

 one, so as to form a thread-like channel at the suture. The enamel 

 rests loosely against the shell and is wrinkled. The exterior is 

 covered by a bluish-black pigment, not easily removed, and the in- 

 terior has a steel-blue or ])lack-lead color. 



This shell, which I found tw^o years in succession in a muddy 

 pool in Cambridge, I thought was sufficiently distinct to be regarded 

 as a new species ; and I accordingly gave its characters, under the 

 name of Limncca chalyhea^ in " Silliman's Journal," xxxiii. 106. 

 But as it has not l)Ocn found in any other place, I am now disposed 

 to regard it as a strongly marked local variety of L. columella. It 

 is very possibly such a shell to which Mr. Say alludes in the " Jour- 



