518 TROOHID^. 



of the shell. The aperture is subquadrate, and broader 

 than, or at least as broad as, it is long ; the interior is 

 silvery white, and not at all grooved; the outer lip is 

 simple, acute, and very oblique; the columella is straightish, 

 white, and devoid of all tubercles, crense, or other mark- 

 ings. The umbilical cavity is white, and in one of the 

 flat varieties is delicately chased with close-set longitudinal 

 lines. In two adult individuals, which each measured 

 seven lines at the base, the length of the conical variety 

 was eight lines, of the depressed variety, barely half an 

 inch. In neither case have we given the extremes ; in the 

 latter form, especially in the young, we have seen examples 

 of which the basal diameter was actually, or all but, twice 

 the length of the shell. In the variety electissimus, the 

 minute longitudinal striulse, that are occasionally visible in 

 the interstitial spaces of the more typical form, appear, 

 when highly magnified, to regularly traverse the elevated 

 sculpture likewise. 



The animal is white, with a yellow tinge, minutely 

 speckled with opaque dots. The head is white and yellow ; 

 its muzzle is broad and crenated at the edge ; the tenta- 

 cula are large, subulate, and, under the lens, minutely 

 ciliated ; they are white, with obscure, dusky rings ; be- 

 tween them are two well-developed, crenated head-lobes, 

 which approach more nearly to each other than those of 

 the next species. The eye-peduncles are stout and rather 

 long ; the eyes are black. The neck-lappets are white ; 

 the inner or columellar lobe has a fimbriated edge, that of 

 the outer one is plain (they are both represented as cre- 

 nated in the figure by mistake). The mantle is even- 

 edged and white with slight dusky markings. The lateral 

 cirrhi are white, with minute lobes at their bases, and are 

 larger than in umhilicatm. The foot is oblong, rounded in 



