Remigum pennae primae tres vix pares. Cauda mediocris, emarginata, rectricibus 12, sub-paribus._

Bill slender, acute, slightly curved, of variable length, base thick, broad, trigonal, the sides compressed; upper mandible near the tip slightly notched; nostrils basal, oval, short, covered by a naked membrane, in the middle of which is an oval aperture; tongue long, bifid, not extensible, the tip fibrous; the three first quills of nearly equal length, and longer than the rest; tail moderate, emarginate, of 12 nearly equal feathers.

Generic Types, Div. 1. _Certhia cyanea, cayana._ Div. 2. _Certhia spiza, &c._ Linn.

SPECIFIC CHARACTER.

_N. (mas.) cyanea; jugulo, dorso, cauda alisque nigris, remigibus margine cyaneo ornatis. (Fem.) Viridis; capite, genis scapulisque caerulescentibus; jugulo cano._

(Male.) Changeable blue; throat, back, tail, and wings black; the quills edged with blue. Female green; head, cheeks, and scapulars bluish; throat grey.

_Male._

Motacilla cayana. _Linn. Gmelin_, 1. 990.

Sylvia cayana. _Lath. In. Orn._ 2. 545. _Gen. Zool._ 10. 655.

Pepit bleu de Cayenne? _Brisson, Ois._ _vol._ 3. _pl._ 28. 1.

Cayenne Warbler. _Lath. Syn._ 4. 502. _Gen. Zool._ 10. 655.

Sylvia Cayenensis caerulea. _Brisson, Orn._ 1. _p._ 455.

_Female._

Motacilla cyanocephala. _Gmelin_, 1. 990.

Sylvia cyanocephala. _Lath. In. Orn._ 2. 546. _Gen. Zool._ 10. 684.

Sylvia viridis. _Brisson, Orn._ 1. _p._ 455.

Le Pepit verd. _Brisson, Ois._ 3. _pl._ 28. _f._ 4.

Blue-headed Warbler. _Lath. Syn._ 4. _p._ 503.

Blue-headed Creeper? _Lath. Syn._ 2. _p._ 727.

Few birds require more ill.u.s.tration than this very beautiful though common species; described by most ornithological writers, but hitherto so little understood, that the two s.e.xes stand as distinct species in a family of birds to which they have, in reality, no natural affinity. According to the Linnaean system it should have been rather placed with the Creepers than the Warblers; an error which has been continued by every subsequent writer, even by Professor Temminck, whose skilful and accurate perception of natural affinities is, in general, so remarkably correct.

That these two birds, however dissimilar in colour, are the s.e.xes only of one species, repeated dissections in their native country have put beyond all doubt; and that it is a genuine _Nectarinia_ (or _Caereba_ of Temminck) will appear from submitting it to a rigorous comparison with the characters the Professor himself has laid down for that genus.

Its habits are no less perfectly the same as the rest of the _Nectariniae_; it is one of the commonest birds of Brazil, and appears spread over the whole extent of that country. It frequents the same trees as the Humming-birds, hopping from flower to flower, and extracting the nectar from each; but this is not done on the wing, because its formation is obviously different from the Humming-birds, which, on the contrary, poise themselves in the air during feeding. The shortness of the bill has evidently given rise to this bird being placed with the Warblers; but this organ is not shorter in proportion than it is in _Nectarinia spiza_, (_Certhia spiza_ of Latham).

I am unacquainted with the other varieties of this species mentioned by authors. Of the bird here described, I have never seen any variety, either in Brazil or in our museums. The young males, as usual before moulting, have the colours of the female; one of them, in an intermediate state, is in my possession. As both the figures are of the size of life, and accurately coloured, a fuller description is unnecessary. The rich sky-blue of the male, in some lights, becomes greenish, and in others dark blue. The bill, like that of all the genuine _Nectariniae_, is slightly notched a little way from the tip, and the base is much broader than high.

Pl. 118

[Ill.u.s.tration]

CONUS Generalis,

_Flambeau Cone._

GENERIC CHARACTER.--See Pl. 65.

SPECIFIC CHARACTER.

_C. testa gracili, fusca, fasciis albidis strigis undatis longitudinalibus interruptis ornata; spirae productae apice acuto, anfractibus concavis, laevibus; basi nigra._

Sh.e.l.l slender, brown, with white bands, interrupted by longitudinal stripes; spire produced, the tip acute, whorls concave, smooth; base black.

Conus Generalis. _Gmelin_, _p._ 33. 75. _var. a._ _Dillwyn_, 359. _var.

a._ _Martini_, _vol._ 2. _p._ 58. _f._ 645, 646. (_dark variety_) _f._ 648 _to_ 652. (_pale varieties_). _Gualt._ 20 _f._ G.

Conus Generalis. _Brug._ _p._ 642. _Lam. Ann._ _vol._ 15. _p._ 363.

It becomes necessary to figure this elegant, but not uncommon Cone, in order to show the young conchologist the little importance that should be attached to _colour_ in the discrimination of species: the figures will likewise point out more fully the distinctions between the present sh.e.l.l, _C. maldivus_, and _C. cinctus_; three species, whose close affinity require ill.u.s.tration.

These relative distinctions may be comprised in a few words; they rest princ.i.p.ally on the spire, which in _C. generalis_ has the upper half much lengthened, slender, and ac.u.minated: in _C. maldivus_ the spire is thick and much shorter: the whorls in both these species are quite plain, and nearly flat: the spire of _C. cinctus_ resembles the last in form, but is deeply concave and striated. These characters are, I think, very satisfactory as specific distinctions.

On the other hand, some attention to these sh.e.l.ls lately, has convinced me that many of the species formed both by Bruguiere and Lamarck should be more correctly considered as varieties; inasmuch as their specific distinctions rest, for the most part, on _colour_ alone: this appears, indeed, to be the leading character selected by these eminent conchologists, and to which, therefore, they have attached the greatest importance. From this opinion, however, I completely dissent; on the principle, that no character which is variable can, with any consistency, be made use of to express permanent distinctions, when not supported by peculiarity of formation or sculpture. The great art in framing the description of a species consists in singling out those characters alone which are most permanent, and exist in every variety of that species; for, when once a character is found to be variable, it no longer becomes a distinction by which a species can be recognised. I consider, therefore, formation and sculpture as the only certain characters of species, and that variation of colour should alone distinguish varieties.

It is therefore not surprising that the specific characters given by MM.

Bruguiere and Lamarck, and resting princ.i.p.ally on the colours of these sh.e.l.ls, are frequently obscure, and always long; two inevitable evils attending every attempt to describe minutely the colour, form, and disposition of the markings of sh.e.l.ls. In justice, however, to these great naturalists, it should be observed, that in this attempt they have done that best which no writer has ever done well.

The spire of _C. generalis_ is generally spotted, and the white band on the margin of the body whorl, more or less crossed by broad waved stripes of a dark brown. It is an inhabitant of many parts of the Indian Ocean.

Pl. 119

[Ill.u.s.tration]

AMPULLARIA globosa,