72 MOLLUSCA. 



In some, the lip of the margin is denticulated externally near the 

 emargination*. 



In others it is entiref. The 



MoRio, Montf. — Cassidaria, Lam. 

 Was separated from Cassis by Montfort. The canal curves less 

 suddenly, and the whole shell leads directly to certain Murices. The 

 animal resembles that of a Buccinum, but its foot is more developed |. 



Tekabra, Brug., 



The aperture, emargination and columella of a true Buccinum; but 

 the general form is turriculated, that is to say, the spire is lengthened 

 into a point §. In the 



Cerithium, Brug., 

 Very properly separated from the Murex of Linnaeus, we observe 

 a shell with a turriculated spire ; the aperture is oval, and the canal 

 short, but well marked, and reflected to the left or backwards. The 

 animal has a veil on its head, and is furnished with two separated 

 tentacula, on the side of which arc the eyes, and with a round, horny 

 operculum. 



Many are found fossil ||. M. Brongniart separates from the Ceri- 

 thia the 



PoTAMiDA, Brongn. 

 Which, with the same form of shell, has a very short and scarcely 

 emarginated canal, no sulcus on the upper part of the right margin, 

 and the external lip dilated. The Potamidpe inhabit rivers, or, at least, 

 their mouths, and fossil specimens are found in strata, which contain 

 other fresh-water or land species only^. The genus 



* Buccinum vibex, Martini, II, xxxv, 364, 365; — B. glaucum, List., 996, 60; — 

 B. erinaceous, List., 1015, 73. 



f The Buccinum of the second division of Gmelin, except the B. echinophorum, 

 strigosum, No. 26, and fyrrhenum, which are Cassidarise. It must also be recollected, 

 that, among the true Cassides, Gmelin appears to have several repetitions. 



+ Bttccinum caudatum, L., List., 940, 36; — jB. echiniphorum, List., 1003, 68; — 



B, strigosum, Gm., No. 26, List., 1011, 71, f. ; — Bucc. tyrrhenum, Bonam., Ill, 160. 

 § The whole of the last subdivision of the Buccina, Gmelin, such as, Buccinum 



maculatum, L,., 846, 74; — Bucc. crenulaium, L. List., 846, 75; — Bucc. dimidiatum, 

 L., List., 843, 71; — Bucc. subula/um, L., List., 842, 70, &c. 



M. de Blainville separates from them the genus subula, which he founds on a 

 difference in the animal, and moreover on the presence of an operculum. 



II Murex vertagus. List., 1020, 83; — M. aluco, List., 1025, 87; — M. annularis, 

 Martini, IV, clvii, 1486; — M. singulafus, lb., 1492; — M. Terehella, Id., civ, 1458, 

 9; — M. fuscatus, Gualt., 56, H; — M. granulatus, Martini, IV, clvii, 1483; — M. 

 moluccanus, lb., 1484, S. &c., with the numerous fossil species described by M. de 

 Lamarck, Ann. du Mus. M. Deshaycs has separated from the Cerithia, under the 

 name of Nevinea, some small species, where the margin is prolonged into the aper- 

 ture, and divides it into three distinct orifices. 



It is also near the Cerithia that we must place several fossil shells, which form 

 the genus Nerinea of M. Defrance, and which is distinguished by strongly marked 

 plicae on each whorl and on the columella, the centre of which, besides, is hollow 

 throughout. Nine species are already ascertained. 



^ See Brongn., Ann. du Mus., XV, 367. In this subgenus should be placed the 

 CmVAium a/n/m, Brug., List., pi. 115, f. 10; — Cer. palustre, f. lb., 836, f. 62; — 



C. muricatum, lb., 121, f. 17, &c., and among the fossils, the Pt'/«ni»rf« LcmarAii, 

 Brongn., Ice. cit. pi. xxii, f. 3. 



