I 



Naticae, Lamellarise, and Velutinse. 53 



rest it is always folded on itself, causing the white tumid part of 

 the rouleau to press the bases of the tentacula against the shell, 

 and thus they obscure the eyes in those species in which they 

 are not obsolete. The upper part of the anterior division of the 

 foot is marked with fine dark longitudinal rather close lines or 

 streaks, behind it is of a pale brown or drab, the reflexed oper- 

 culigerous lobe is white, and the entire disk of the sole pale 

 yellowish white. The animal has the power of stowing entirely 

 out of sight the enormous mass of foot ; it does so very delibe- 

 rately, and closes the aperture effectually by placing the strong 

 corneous operculum well within the margin ; it has nothing of 

 the rapid retraction of the foot, as in Rissoa. 



These animals abovmd of large size in the Warren Sands, 

 opposite Exmouth. When they are just taken, in vigour, and 

 immersed in sea-water, it is scarcely possible to contemplate a 

 more beautiful and interesting object, with its shell rising as a 

 globular pyramid from an immense circular disk, elegantly 

 marked with fine dark lines on a clear di*ab ground. I recom- 

 mend this species for examination ; its large size affords a good 

 view of the external organs, and the anatomy is comparatively 

 facile. 



Natica nitida, Brit. Moll. 

 Natica Alderi, nonnuU. 



This species, as regards the external organs, is so similar to 

 the N. monilifera, that a notice of the variations will suffice. It 

 has, like its congener, the extended anatomy of which has been 

 omitted to save space, two branchial plumes, and the mucous fillets 

 are nearly as evident as in the Muricidce. In the male, the organ 

 of reproduction is in every respect more developed. The eyes 

 are distinctly visible, immersed in the centre of the anterior bases 

 of the tentacula. The colour of the upper front surface of the 

 foot and tentacula is a deepish dull red-brown, which is deposited 

 on the first-named organ in close irregular longitudinal streaks, 

 but on the posterior portion they are less close and paler coloured, 

 and still less so laterally ; the sole is a uniform pale yellow : these 

 animals vary much in the general colour, but whatever the 

 ground colour may be, it is thus modified on the particular parts 

 as above stated. 



The animal is active and not uncommon in the coralline zone 

 at Exmouth, where, though very rarely, the pure snow-white 

 variety occurs, as well as the plain chestnut-coloured N. sordida, 

 which is probably not distinct from the present animal. The 

 other British species we have not met with alive are theiV. Mon- 

 tagui, N. Gromlandica, which is the N. pusilla of Gould, and the 

 'N. helico'ides; this latter is quite unknown to us, as is the 

 JV. Kingii. 



