Shell solid, thick, more or less globular, flat beneath, spire but little, if at all, projecting, not umbilicated; aperture large, semilunar, very entire; the external margin very much hollowed; the internal or columellar straight, sharp, and shaped like a partition, often dentated; operculum horny or calcareous, sub-spiral; the summit entirely marginal at its extremity, implanted by teeth more or less marked, and sunk in the columellar margin, on which it seems articulated. Nerita exuvia. N. textilis. N. undata. N. peloronta. N. chlorostoma. N. atrata. N. polita. N. albicilla. N. chamæleon. N. versicolor. N. Ascensionis. N. Malaccensis. N. lineata. N. scabricosta. N. plicata. N. tessellata. N. signata. _N. peloronta._ The bleeding-tooth Nerita. Pl. 21, fig. 5. Thick, transversely sulcated; inner lip with two crenulations, with a bloody mark at their base; under lip with two notches near its internal upper edge; colour yellowish, tinged with red, with variously coloured bands. _N. exuvia._ The exuvia Nerita. Species with the inner lip toothed and tuberculated. _N. polita._ The smooth Nerita. Species with both lips toothed; beautifully distinguished by having three or four bright crimson bands, on a dark mottled ground, running in a parallel direction with the convolutions of the shell. A favourite Indian ornament. 4. Natica. Thirty-one species. A marine shell, formerly classed with the Nerita, but distinguished by being without teeth, and having an umbilicus modified by the callosity. Shell smooth, rather thin, and not covered with epidermis; the spire evident, though low, umbilicated; the columellar edge not toothed, more or less callous, modifying the umbilicus; the right edge thin and not toothed interiorly; operculum calcareous or horny and smooth, semi-spiral, with concentric ribs fitting into a slight groove on the columella.