Linnæus under the Nerita genus comprehends as well the imperforated or non-umbilicated kinds as those which have that perforation. The later continental writers divide these again, retaining the name Nerita to those which have no perforation; those with a perforation are called Natica, by the french authors Natice, after Adanson, Gualtieri, and Favanne. Lamarck has also a genus Neritina, and another Navicella, all which in the Linnæan system are of the Nerita tribe. Nerita Polita is by no means an uncommon shell upon the coasts of the Indian Ocean, being found throughout their whole extent from Japan to the Cape of Good of Hope, and as it appears also upon the shores of many islands in the Indian and the Great Southern Ocean. Besides being so very abundant in those parts, it may also be observed that no species of the testaceous tribe is more remarkable for the almost endless variety of colours, or the form and disposition of the spots, dots, and lineations, than the individuals of this kind of Nerit. There are, however, some few of its varieties which from being local are far less abundant than the rest, and the shell in particular which we have selected for the most conspicuous object in the annexed plate is one the most important of the number. The prevailing colour of the ordinary varieties is olivaceous, in some paler, in others more inclining to blackish; the charactered marks in general yellowish, triangular or sagittate, and varied with short blackish lines. This is the usual appearance of the back or upper part of the shell, the region surrounding the mouth is white, including the lip, the inside of the mouth yellow, and this latter character appears constant throughout all the varieties of the species. The particular variety which constitutes the chief object in our plate, is of the red banded kind, the bands being diversified with red and white, disposed in spots, and lineations, with peculiar elegance. The varieties of this banded kind are scarce in general, but the particular kind which we have represented is unique, whether regarded for its magnitude, its exquisite perfection, or brilliancy of colouring. We have represented the upper and under surface of this shell, together with the upper and under surface of a shell of the common kind, in order that by the contrast, the beauty of the former might be exemplified with greater perspicuity.