140 DONAX. 



occurring in different parts of the whorls, do not form the con- 

 tinuous ridges which characterize the generality of the Ranellee. 



DISCORBITES. Lam. A genus of microscopic Foraminifera. 



DISTANT. The teeth on the hinge of a bivalve shell are said to be 

 distant when they are remote from the umbones. 



DIVARICATED. Diverging, meeting in a point, as the teeth on 

 the hinge of Placuna, fig. 184. 



DOLABELLA. Lam. (Dim. from Dolabra, a hatchet.) Fam. 

 Aplysiacea, Lam. and Bl. — Descr. Hatchet-shaped, arched, 

 covered with a horny epidermis ; posteriorly attenuated, thick- 

 ened, sub-spiral, anteriorly plane, broad, thin ; posterior margin 

 reflected. — Obs. The two or three species of Dolabella known are 

 inhabitants of the Indian Ocean. They were placed by Linneeus 

 in his very convenient genus Bulla, under the name B. dubia. 

 Fig. 255, Dolabella Rumphii. 



DOLIUM. D'Argenville. (a tun.) Fam. Purpurifera, Lam. En- 

 tomostomata, Bl. — Descr. Thin, ventricose, oval, or globular, 

 with a short spire ; large aperture terminating in a reflected canal, 

 and spirally ribbed or grooved external surface ; outer lip cre- 

 nated ; inner lip reflected over part of the body whorl, which 

 terminates in a tumid varix ; epidermis light, horny. Mediter- 

 ranean and East Indian. — Obs. This genus is distinguished from 

 Cassis by the outer lip, which is not reflected. The species which 

 are not so rotund as the others, as D. Perdix, Auct. have been 

 separated under the name Perdix, as generic. Fig. 420, Dolium 

 Maculatum. 



DONAX. Auct. Fam. Nymphacea, Lam. Conchacea, Bl. — Descr. 

 Equivalve, inequilateral, trigonal, with the anterior side short, 

 straight, plane ; the posterior side elongated, drawn to a narrow, 

 rounded termination ; hinge with two cardinal teeth in one valve, 

 one in the other, and one or two, more or less remote lateral teeth ; 

 ligament external ; muscular impressions two in each valve ; pal- 

 leal impression sinuated posteriorly. — Obs. The Capsse have not 

 the crenated margins, the short anterior side, and the distinct late- 

 ral teeth, which characterize the Donaces. Some species of Erycina 

 resemble Donax in general form, but are at once distinguished 



