Volume I Part 13 (2/2)
ACHATINA marginata.
_Marginated Achatina._
GENERIC CHARACTER.
_Testa ovata, vel oblongo-ovata, spira elevata, apertura subovale.
Columella laevis, simplex, ad apicem truncata; labium externum tenue, internum inflexum integrum; umbilicus nullus._
Typus Genericus _Bulla Achatina_. Linn.
Sh.e.l.l ovate, or oblong-ovate; spire elevated; mouth nearly oval.
Columella smooth, simple, truncated. Outer lip thin; inner lip entirely inflexed. Umbilicus none.
Generic Type _Bulla Achatina_. Linn.
SPECIFIC CHARACTER.
_A. testa ovato-oblonga, strigis inaequalibus ferrugineis; spira ad apicem obtusa, 5-voluta; sutura depressa linea sulcata marginali._
Sh.e.l.l ovate-oblong, with irregular ferrugineous stripes; spire obtuse at the top, of five volutions; the suture depressed, with a marginal indented line.
_Lister_ 579. _fig._ 34. _Gualt. pl._ 45. B. _Knorr_, _vol._ iv. _tab._ 24. 1. (badly coloured.)
The largest sh.e.l.ls. .h.i.therto discovered as inhabiting the dry land belong to this genus, inst.i.tuted by the celebrated Lamarck, but still divided by the strict followers of Linnaeus between the _Bullae_ and _Helices_, with a singular infelicity of even artificial arrangement. The simple characters peculiar in a greater or less degree to all, will readily distinguish them; and I apprehend most of the species of the first division (which includes the present) will be found to inhabit only the African continent, while _Bulla virginea_ and the smaller sh.e.l.ls placed in the second division are found princ.i.p.ally in the new world; where also two or three gigantic species of _Bulimus_ occupy the place of the larger African _Achatinae_.
Of these, the sh.e.l.l now figured is one of the rarest, and has. .h.i.therto been overlooked as a variety of the Linnaean _Bulla Achatina_; the colour of both is subject to much variation; but this will be found at best a most indecisive and vague character for specific distinction when unaccompanied by others more important and connected with the formation of sh.e.l.ls. I have therefore not hesitated in making this a distinct species, from having had the means of examining at different times near twenty specimens, all of which presented the following characters. Spire of five whorls, the last or terminal one very small and flattened; the apex obtuse; the suture depressed, as if flattened on the sh.e.l.l, and margined by one or sometimes two indented lines, parallel, and at the top of each whorl. In the colour of its mouth it varies in sometimes having a tinge of rose-colour at the base and top of the spire, but the mouth is more generally white. The body whorl is more or less ventricose; the outer lip is a little reflected, and the whole sh.e.l.l, when full grown, much thicker and heavier than any of the other species. The epidermis is yellowish-brown, beneath which the sh.e.l.l is nearly white, beautifully marked with broad remote stripes of chesnut, with others more slender (and sometimes broken into spots) between. I have another specimen which agrees tolerably with Lister's figure in being more than usually ventricose, and which I think is accidental. The only constant variety appears to be that figured by Knorr, ii. tab. 3. fig. 1. having the spire entirely rose-colour.
The marginal line and the correct number of whorls in the spire are well expressed in the figures of Lister, Gualtieri and Knorr. The first of these figures is accidentally more ventricose; the second, like all the other figures of Gualtieri, is defective at the apex; and Knorr's I suspect has been outrageously coloured from the real pink-mouthed _Achatina_.
It inhabits the coast of Guinea; and I am informed the animal is eaten by the natives.
Pl. 31
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