Lamarck first separated the shells comprised in this genus from the Volutes of Linnaeus; their principal distinction rests in the formation of the outer lip, which has a very thick margin, more or less toothed on the inner rim; the base likewise is nearly entire, and the inner lip quite wanting. By these peculiarities, the _Date Shells_ are easily known from the _Volutes_ on the one hand, and the _Cowries_ on the other; and the invaluable researches of M. Adanson, who has described and figured the animals of each of these genera, has established this distinction on the most solid principles; it will, however, be interesting to trace, by the shells only, how beautifully this arrangement is developed. The _Marginellae_ may be divided into two sections; the first bearing in form and habit a strong resemblance to the _Cypraeae_, and the second gradually losing these indications, and acquiring those of the spiral _Volutae_. Among the first are several species, which, like the Cowries, appear destitute of any spire (as in _M. cingulata_); this part, however, begins to show itself in other successive species very progressively, until it becomes elevated and defined in _M. glabella_. This shell may be considered the passage to the second division, in which the species lose the simple oval form of the first, and acquire a contracted base and pointed spire, perfectly resembling _Voluta undulata Lam._ and its allies. The extreme developement of these characters is shown in _M. faba_. This genus must, then, be considered as connecting those of _Cypraea_ and _Voluta_ (Lam.); excepting one, the whole of the species are very small; and as the three here selected to illustrate these remarks are frequently seen, and have been often described under other names, little more is necessary than to detail their specific characters. * * * * * MARGINELLA cingulata, _Banded Date Shell--upper figures._ _M. testa ovata, albida, lineis aurantiacis fasciata; spira obsoleta, umbilicata; columella 6 plicata._ Shell oval, whitish, banded with orange lines; spire obsolete, umbilicated; pillar 6 plaited. Voluta cingulata. _Dill._ 525. 56. _Lister._ 803. _f._ 9. _Martini_, 2. _t._ 42. _f._ 419 _and_ 20. _Gualt._ _t._ 25. _c._? 28. _b._ _Adanson_, _t._ 4. _f._ 4. * * * * * I am happy to record Mr. Dillwyn as the first systematic writer who separated this from _Mar. persicula_, which has reddish spots, and is quite a distinct species. The present is a pretty, though common shell, and observed by Adanson in great plenty on the African coast. * * * * * MARGINELLA prunum, _Grey Date Shell--middle figures._ _M. testa ovata, grisea, immaculata; spira parva, conica; apertura fusca; columella 4 plicata._ Shell oval, grey, immaculate; spire small, conic; aperture brown; pillar 4 plaited.