NATICA. 177 



upon its edges the two tentacles; eyes are either wanting 



or rudimentary behind the veil ; the operculum, whether of 



shell or horn, is half-circular and has a small flat spire. The 



shells are smooth, rounded, with small spires of few whorls ; 



the aperture is half-circular, with its inner edge nearly 



straight; behind the columella is a hollow, or umbilicus, 



which is sometimes wholly or partially concealed by the 



spreading callus, or swelling of the columella. Our species : 



JV. moniliferay with the shell very globose, with the whorls 



arching suddenly from the sutures; it is of a dull 



greyish or fleshy tint, with a single band of brown, 



squarish marks ; operculum horny. Animal yellowish, 



tinged w- ith purple ; the foot is capable of very great 



expansion, and the head, is furnished wdth very small 



eyes. 



iY. nitida has a smaller shell, sometimes marked all over 



wdth bands of spots, and the whorls shelve tow^ards the 



suture, so as to produce a more tapering spire. The 



animal is faintly yellowish, spotted with greyish-brow^n. 



Its habits are not so much to burrow in the sand as to 



throw up Htile hillocks of it, in which to hide until 



the tide returns. 



iY. sordida : the shell is not so tapering as iY. 7iitida, nor 



N 



