1870.] On the Land Sheik of Bourbon. 407 



B. Nanina argentea, Ev., Cone. Icon. No. 1434. I should fancy 

 this must be the oldest, or nearest to the original type, from almost 

 perfectly similar forms being found in both the sister Islands, 

 under circumstances that would seem to preclude the possibility of 

 its having been introduced into either. In form it is very close to 

 the preceding, but the last whorl is more dilated, not compressed, 

 the sharp keel not visible on the other whorls ; it is finely striated. 



C. Nanina implicata, n. sp. Closely allied to N semicerina 

 M o r 1 1. ; it differs by the whorls being rounder, more convex, the 

 keel in consequence almost rudimentary; the green band of the 

 epidermis round the umbilicus is a little broader, without the 

 conspicuous brown stripe next the suture, in its place the same 

 green epidermis, as round the base, forms two bands in the centre 

 of each whorl, the lower one being broad and distinctly marked 

 throughout, the upper one indistinct and interrupted, only clearly 

 developed in the last whorl ; the apex is more obtuse, but the 

 most characteristic distinction is the absence of the coarse, regular 

 striation, N. implicata being perfectly smooth ; the proportions of 

 the two species are almost exactly the same. 



In the style of colouring, it somewhat resembles N. argentea, it 

 can, however, be easily distinguished by its more depressed and 

 concave whorls, on the last of which, there is an almost impercepti- 

 ble keel. 



-'Bare ; Peter Botte Mn. Mauritius. 



D. Nanina semicerina, Morlt., Bev. Zool. 1851, p. 219, 

 (Rawsonis, Bens.). Locally abundant at Mauritius on shrubs, &c, 

 in very damp woods. This handsome shell varies considerably in 

 colouring, the whorls are a little less concave than in the last, the 

 keel on the last whorl a little more developed ; it is the most 

 strongly striated species of the group. 



Animal whitish, neck mottled with black, tentacles grey. 



13. Nanina argentea, E v. 



I have already spoken of the affinities of the shell of this species ; 

 the animal is of a pure white, the front of the neck having a 

 faint yellow tinge, the tentacles are orange with dark grey streaks ; 

 the tail is sharply truncated, near it there is a mucous pore with a 



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