Volume I Part 17 (2/2)

The species of this and one or two other genera of land-sh.e.l.ls are subject to such variability in their colouring, that it becomes extremely difficult to ascertain which are species and which varieties. The sh.e.l.l now figured might, on a cursory glance, very well pa.s.s for one of the Protean varieties of the Linnaean _Bulla fasciata_; but a comparison with that sh.e.l.l will at once point out the strong specific difference that exists between them in the formation of the mouth. In this, the lower half of the inner lip, or more properly the pillar, is nearly straight; the base entire, or without any notch or truncated appearance: whereas in the true _A. fasciata_, the inner lip at the base is very much curved inward, and notched before it joins the outer lip. The mouth is also short and broad: whereas in this it is much more oblong, and the base round. Other more obvious characters exist in the form of the whorls, spire, and more particularly in the colour, of these two sh.e.l.ls; but these are in comparison of minor importance.

I regret having but one example of this sh.e.l.l, as it prevents me from tracing how far the characters here detailed hold good in other specimens.

They are such, however, as, I think, fully to justify the propriety of considering it a species.

Its locality is unknown.

I have little doubt more than one species exist among the supposed varieties of the true _Bulla fasciata_ of Linn., which I take to be the sh.e.l.l figured by Lister.

Pl. 42

[Ill.u.s.tration]

OLIVA Braziliana,

_Brazilian Olive_

GENERIC CHARACTER.

_Testa cylindrica, polita; spira conica, ac.u.minata, brevissima; labium exterius simplex, interius incra.s.satum, tumidum; columella plicis numerosis gracilibus; apertura basi truncata, emarginata._

Typus Genericus _Voluta Porphyrea_ Lin.

Sh.e.l.l cylindrical, polished, spire conic ac.u.minated, very short; outer lip simple, inner lip thickened, tumid, columella with numerous slender plaits, aperture at the base truncatedly emarginate.

Generic Type _Voluta Porphyrea_ Lin.

SPECIFIC CHARACTER.

_O. testa coniformi, lata; apertura effusa, labio interiore tumida callositate super spiram extendente._

Sh.e.l.l coniform, broad; aperture effuse, tumid callosity on the inner lip large, and spreading over the spire.

Oliva Braziliensis. _Martini p._ 130, _tab._ 147 _&_ 8, 1367 _&_ 8.

Oliva Braziliana. _Lamarck._

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