532 trochid^:. 



at the first glance, that we hesitated to regard them as 

 belonging to the same species, yet so intimately connected, 

 that when we examine a long series of specimens from 

 various localities we cannot separate them with precision. 

 The one is peculiarly oblique and depressed, with a very 

 expanded outer lip, and the rest of its features modified to 

 correspond with the general contour ; the other is for more 

 globular, and reminds us a little by its shape of the common 

 Valvata (piscinalis). 



The species is small, shining, translucent, smooth, except 

 some minute and indistinct impressed spiral lines upon the 

 base, and so thin that the internal nacre is visible through 

 the external colouring, imparting to its horn-like hue a 

 beautiful bronze-like lustre. For the most part two rather 

 broad but undefined bands, of a deep flesh-like tint, encircle 

 the body, the upper one of which is below, but not adjacent 

 to, the suture ; the lower, and less distinct one, is just 

 above the basal circumference : occasionally they unite, so 

 as merely to show a pale sub-sutural line upon the terminal 

 volution. The shape, as we before remarked, is very 

 variable, ranging from obliquely suborbicular to orbicular- 

 conoid; the spire, however, is always a little raised, but 

 its apex, though small, is blunt, and the apical volutions 

 are rather depressed ; the lateral outline is subrectilinear, 

 or a little arched. There are five whorls, which rapidly 

 enlarge ; the body, or final volution, is disproportionately 

 ample, and, as well as the penult, is more or less ventricose ; 

 their slope, in the more depressed variety, is very gentle, 

 but becomes more considerable in the subconoid one : the 

 sutural line is delicate. The base is more or less com- 

 pressed, but is slightly convex. The umbilicus is rather 

 large and profound ; it is not bounded by any angular 

 ridge, but is moderately shelving. 



