- Testa ovata. Spira brevissima aut nulla. Labium exterius crassissimum, margine interiore crenato. Columella plicata. Basis subintegra. Animal capitatum, capitis fronte profundè emarginato; oculis ad tentaculorum 2 subulatorum basin externam adsitis; tubâ jugulari simplici; pede magno, foliaceo, ponè attenuato; penulâ dilatatâ, testæ latera obtegente.
Typ. Gen. Volutæ perspicula, glabella, prunum, &c. Lin.
- Shell oval. Spire very short or concealed. Exterior lip very thick, with the internal margin crenated. Pillar plaited. Base nearly entire. Animal capitate; head notched in front, with lengthened, pointed tentacula, at the external base of which are the eyes; neck with a simple tube; foot large, foliaceous, pointed behind; mantle dilated, and folded over the sides of the shell.
Generic Types Vol. perspicula, glabella, prunum, &c. Lin.
Lamarck first separated the shells comprised in this genus from the Volutes of Linnæus; 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 Marginellæ may be divided into two sections; the first bearing in form and habit a strong resemblance to the Cyprææ, and the second gradually losing these indications, and acquiring those of the spiral Volutæ. 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 Cypræa 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.
Banded Date Shell—upper figures.
- M. testâ ovatâ, albidâ, lineis aurantiacis fasciatâ; spirâ obsoletâ, umbilicatâ; columellâ 6 plicatâ.
- 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.
Grey Date Shell—middle figures.
- M. testâ ovatâ, griseâ, immaculatâ; spirâ parvâ, conicâ; aperturâ fuscâ; columellâ 4 plicatâ.
- Shell oval, grey, immaculate; spire small, conic; aperture brown; pillar 4 plaited.
- Voluta plumbea. Sol. MSS. L'Egouen. Adanson, tab. 4. f. 3.
- V. prunum. Gm. p. 3446. 33. Martini, 2. t. 42. f. 422 and 3. En. Meth. 376. 8. Lister, 817. 28. (young.) Dill. 530. 69.
The plaits are very strong, and, together with the outer lip, white; equally common, and from the same country, as the last.
Fly-spot Date Shell—lower figures.
- M. testâ ovatâ, plicatâ, fulvâ, punctis fuscis ornatâ; spirâ conicâ; basi emarginatâ; columellâ 4 plicata.
- Shell oval, plaited, fulvous, with brown dots; spire conic; base notched; pillar 4 plaited.
- V. faba. Gm. 3445. Lister, 812. 22. Martini, 2. t. 42. f. 431? 432, and 3. En. Meth. 377. 1. Gualt. 28. Q. Dill. 528. 63.
The whorls of this pretty shell are plaited into little nodules; it is usually very small. The supposed variety figured by Martini, and mentioned by Mr. Dillwyn, I am inclined to believe, may be a distinct species.