282 TELLINIDiE. 



duced to draw up a more diffuse description of it than is our 

 wont with species of such undeniably foreign extraction. 



Its general shape is more or less oblong, and the texture opaque 

 and tolerably strong. The valves are somewhat ventricose or de- 

 cidedly convex ; the profundity is, however, chiefly apparent 

 upon the subumbonal region ; they are but little inequilateral, 

 and covered with a shining olivaceous yellow or buft-coloured, 

 somewhat corneous epidermis, beneath which the shell is whitish, 

 and more or less clouded with violet stains, which latter are, in 

 the immature examples only, arranged in concentrically-disposed 

 flexuous lines ; at this stage, too, there are a pair of paler very 

 narrow rays at no great distance from the posterior extremity. 

 The surface is almost smooth ; there are often, however, a few 

 antiquated concentric lines in front near the lower margin, and 

 almost always some rather closely-set inferior subimbricated 

 concentric lines upon and beyond the rather obscure umbonal 

 ridge. The ventral margin, which is moderately convex (but 

 not arcuated) in front, rises obliquely and rather considerably 

 upon that side, becoming nearly straight or very slightly inflected 

 near its posterior termination. Both dorsal edges are subrecti- 

 linear ; the front one, which in the young is slightly convex, but 

 becomes flattened down with age, slopes in a very trifling degree ; 

 the hinder one, which in aged specimens is somewhat retuse and 

 moderately sloping, declines but little in the younger examples. 

 The anterior side is rather the longer, and tapers but little at its 

 extremity, where it is obliquely rounded off below, but is sub- 

 angulated above ; the front margin is curved, and its chief swell 

 is above the middle. The posterior termination, which becomes 

 almost wedge-shaped in the adult, where the tip, however, is 

 always rounded off, is in the younger shell (whose extremity is 

 not more attenuated than in front) very obtusely and indistinctly 

 subbiangulated ; in this stage, its chief swell is below the middle 

 of the side, and the narrow tip is subrectilinear. The umbones 

 do not appear prominent (they arc generally a little eroded) nor 

 the beaks acute ; the ligament is Avanting in all the specimens 

 we have examined, but judging from the rather projecting nyra- 

 phal callosities, must be of both moderate length and projection. 

 There is no appearance of a lunule ; the hinder dorsal surface 

 seems linearly sunken (as in most of the Donaces). The interior 

 is glossy, and more or less mottled with violet ; the edge is quite 



