* Ex albo rubro nigroque variegata. NERITA POLITA: testa lævi: vertice obliterato, labio utroque dentato. _Linn. Mus. Lud. Ulr. 678. n. 392._ _Linn. Syst. Nat. edit. 12. 2. 1254. 731._ _Gmel. Linn. Syst. 6. 3680. 43._ NERITA POLITA. _Chemn. 5. t. 193. f. 200. 2014._ _Rumpf. Mus. t. 22. fig. 1. k._ _Argenv. Conch. t. 7. f. k._ _Seba Mus. 3. t. 38. f. 56._ _Lamarck T. 6. p. 2. 192. 7._ * * * * * In the arrangement of Cuvier, entitled “_Règne Animal_,” the Mollusca or animal of the Nerita constitutes one of his “_Gasteropodes pectinibranches_,” the character of which as defined by that author is quite as comprehensive and rather less explicit than the Linnæan limaces: he divides them into several families according to the peculiar form of their shells, for collectively almost every genera of the spiral univalves fall under this very general denomination, as well as many of those shells which are simply conic, as in the Linnæan classification they do under that of Limax. Cuvier mentions as a character of this tribe that their breathing apertures, with the exception of a family he calls Cyclostomes, are composed of a number of foliations ranged parallel to each other like the teeth of a comb. They have two feelers, and two eyes usually situated on a pedicle. The greatest difference between these animals consist in the presence or absence of the canal formed by a prolongation of the edge of the pulmonary cavity of the left side, a respiratory organ communicating with others by means of which the animal breathes without quitting its retreat in the water. According to Lamarck the animal of Nerita has the foot large and short, with two pointed feelers, and the eyes raised upon a papilla at the exterior base of each. Bosc is less diffuse than either. The animal of the Nerites, he observes, have the head flat and lunate, a little sloping to the two extremities: from the base of the head on each side issues two conic slender horns, one of which is twice the length of the other. The eyes are two little black points placed upon a trihedral tubercule at the exterior base of the horns, the mouth placed underneath the head and formed with a lip, thick and wrinkled. The foot almost round, flat beneath, convex above, and rather shorter than the shell. The mantle or fleshy prolongation entirely covers the interior of the shell and is slightly crenulated at the margin. Denys de Montfort speaking of the species Nerita Peloronata, a shell abounding on the shores of the Antilles, observes that there are male and female animals of this kind, the two sexes being isolated or distinct individuals; they are of an amphibious nature, living in the sea, from whence they ascend occasionally and crawl about the rocks.