SPECIFIC CHARACTER.

_A testa ovata, rugosa, epidermide olivaceo-fusca; labio exteriore tenui; apertura alba; umbilico vix clauso._

Sh.e.l.l oval, wrinkled; epidermis olive-brown; outer lip thin; aperture white; umbilicus nearly closed.

In prosecuting my ill.u.s.trations of this genus, I have carefully examined all the specimens in the cabinets of my friends, and have added many to my own. These materials have thrown some additional light on those species which I have already described, and have enabled me to detect several others altogether new. Among the latter is the sh.e.l.l here figured, and which is so rare, that I know but one example of it in this country. Its form is more oval than that of _A. rugosa_, from which it is likewise distinguished by a very small umbilicus, nearly concealed by the inner lip; the wrinkles are numerous and unequal, the spire pointed, and the aperture milk-white.

Since my remarks on the _Planorbis cornu-arietis_ of Lamarck were published, it has been discovered that the sh.e.l.l is furnished with an operculum: one of these is in the possession of Mr. Sowerby: thus what was a matter of doubt becomes a fact, and affords the only substantial argument for terming it an _Ampullaria_. On the other hand, its affinities to _Planorbis_ (marked by its discoid, depressed form, and the total absence of the pillar,) remain in no degree impaired. The weight of argument on both sides _now_ appears to be so equal, that it is a matter of no moment whether this sh.e.l.l be placed in the system at the end of the _Ampullariae_, or at the commencement of the _Planorbes_. To the generality of conchologists, the latter collocation would appear the most simple; but, on the whole, I incline more to the propriety of considering it the terminal species of the _Ampullariae_, or that which marks their transition (as I before observed) to the _Planorbes_.

Pl. 176

[Ill.u.s.tration]

ANODON elongatus,

_Lengthened Anodon._

GENERIC CHARACTER.--See Pl. 96.

SPECIFIC CHARACTER.

_A. testa transversim oblonga, cra.s.sa, antice compressa, extremitate utraque rotundata; umbonibus valde prominentibus, cra.s.sis; lamina cardinali convexa._

Sh.e.l.l transversely oblong, thick, anteriorly compressed, both extremities rounded; umbones very prominent, thick; hinge-plate convex.

This extremely rare sh.e.l.l bears not the least resemblance to any which Lamarck has described, or with which I am acquainted. It was formerly in the late Mr. Forster's collection, and is now in the possession of Mrs.

Mawe. Its form is like that of _Unio ovatus_ (_Mya ovata_ of Montague), but it is a much thicker and stronger sh.e.l.l; the posterior end is greatly compressed, but round; the umbones convex, remarkably thick, and deeply eroded; the inside pearly and iridescent, with a strong flesh-coloured tinge; the ligamental or hinge-plate is perfectly smooth, and rather convex; the muscular impressions are deep.

One valve of the specimen above alluded to (the only one I have seen), is uncoated, and beautifully iridescent. Its country is unknown--but I think it may prove a native of the South American rivers.

Pl. 177

[Ill.u.s.tration]

TURBINELLUS spirillus,

_Carinated Turnip Sh.e.l.l._

GENERIC CHARACTER.

_Testa pyriformis vel fusiformis, sub-ponderosa. Apex papillosus.

Columella plicata. Labium interius margine dilatatum. Ca.n.a.lis elongatus, rectus._

Sh.e.l.l pear-shaped or fusiform, heavy. Apex papillary. Pillar plaited.

Interior lip with the margin dilated. Ca.n.a.l lengthened, straight.

Generic Type. _Voluta Pyrum._ Lin.

SPECIFIC CHARACTER.

_T. pyriformi; spira depressa, apice prominente; anfractu basali carinato; labio interiore dilatato, albo; columellae basi plicata._

Sh.e.l.l pear-shaped; spire depressed, apex prominent; basal whorl carinated, interior lip dilated, white; base of the pillar one-plaited.

Murex spirillus. _Gmelin_, 3544. _Dillwyn_, 721.

_Martini_, 3. _tab._ 115. _f._ 1069. _Knorr_, 6. _tab._ 24. _f._ 3.

_Pyrula Spirillus._ _Lam. Syst._ 7. _p._ 142.

In a.s.signing a situation, under the modern system, to the _Murex spirillus_ of Linnaeus, no genus appears to me more adapted for its reception than that of _Turbinellus_. These sh.e.l.ls were formerly blended with the Linnaean Volutes, but are now detached from them as a distinct genus. The most striking peculiarity consists in the prolongation of the base into a long and straight ca.n.a.l; they possess, in common with the Volutes, a papillary spire, and, in general, their surface is smooth. There are, however, other sh.e.l.ls cla.s.sed by the French conchologists with this genus, from their having a plaited columella; in these, the apex of the spire is acute, the base truncated, and the outside rough with nodules or obtuse spines; characters so greatly at variance, and so very distinct from those first mentioned, that it becomes questionable whether these latter sh.e.l.ls should not rather be cla.s.sed as a distinct group: in fact, they are much more nearly allied to _Mitra_ and _Cancellaria_, which have acute spires, sculptured volutions, and truncate bases, than to the smooth _Turbinelli_, which differ so strikingly in all these particulars.

This sh.e.l.l is common to many parts of the Indian Ocean; and, like most of the smooth _Turbinelli_, has the inner lip dilated.

Pl. 178

[Ill.u.s.tration]

BUCEROS coronatus,

_Coronated Hornbill._

GENERIC CHARACTER.