opposed to the third and fourth, and the longest (or representative of the middle toe in the generality of birds) is accordingly inward. It also includes certain genera (as the touracos and puff-birds) which have the first and fourth toes disposed laterally, and one (that of the colies) generally described to have all four toes directed forwards. By stating that the tarse is always scutellated in front, we succeed in excluding the parrots from the definition; and the syndactyle jacamars, by mentioning that the forward toes are separate from the first joint. I am aware of no further generalization that can be advanced, apart from other Strepitores; unless it be that the young appear, without exception, to shed their entire nestling plumage during the first autumn or winter.

The Zygodactyli primarily subdivide into two very distinct groups, which I have termed Picoides and Cuculoides.

The Picoides are distinguished by having the muscular coat of the stomach more developed, and by the absence of cœca to the intestine: the sternum is always doubly emarginated at its posterior border, and the coracoid bones are of unusual length. All of them produce purely white eggs; and the young (I have reason to suspect) are in every instance hatched naked. The clothing feathers possess an accessory plumelet, more or less developed.

In the Cuculoides, the stomach is comparatively lax; and there are large pedicillate dilated coca, resembling those of the owls, as in all other Strepitores that have any: the sternum is sometimes only singly emarginated, and the coracoid bones are stout, and never elongated. Many of them lay coloured or spotted eggs; and probably all (like our native cuckoo) are hatched covered with down. The clothing feathers exhibit not the slightest trace of a supplementary plume. It may be added that the brain is remarkably diminutive, which is not the case in the Picoides.

The former of these divisions is especially remarkable for the variations which it presents in the structure of the tongue, which is barbed like a feather in the toucans, vermiform and protrusile, with generally some small retroflected lateral spines near the tip, in the woodpeckers, and of the ordinary shape in the barbets. The great majority of its species display bright colours. They fall under two principal and very distinct minor groups, which I have designated Levirostres and Cuneirostres. The latter contains the only scandent members of the Zygodactyli, although the entire group (with the addition even of the jacamars and trogons) is still denominated “grimpeurs" by the French. We must now confine our attention to the Levirostres.

Under this appellation I have brought together the two very distinct families of Rhamphastide (comprising the toucans and aricaris), and Musophagida (consisting of the plantain-eaters, touracos, and colies); the former restricted in its distribution to South America; the latter peculiar to the eastern hemisphere, and with the exception of two or three species of coly, to Africa. The name, if not quite all that may be wished, is nevertheless the least objectionable that has yet occurred to me: it is appropriate enough to all except the colies. There is considerable similarity in the conformation of the skeleton in these two families, the principal difference consisting in the very small size of the sternum throughout the Musophagide, and in the imperfection of the clavicles, or lateral halves of the furcula, in the true toucans, though not in the closely allied genus of aricaris (Pteroglossus), to judge from l'Herminier's representation of the sternal apparatus of Pt. aricari, wherein the furcula is made to resemble that of a touraco: in both, there are no false ribs attached to the anterior anchylosed vertebra of the pelvis, a very peculiar character. The beak is inflated and permeated by osseous fibres in the plantain-eaters (Musophaga), and to a less extent in the touracos (Corythaix) and nape-crests (Chizeris); with proportionally thin parietes, as in the toucans (Rhamphastos), where the inflation and consequent attenuation of its substance attain their ultimatum. The tongue, which in the toucan family is barbed throughout its length with lateral appendages like a feather, is in the touracos similarly fringed, but towards the tip only, to a variable extent. The digestive organs chiefly differ in the presence of a small gall-bladder in the Musophagide, which is wanting in the Rhamphastide. Lastly, of their external characters, it may be remarked that both have only ten tail-feathers, that their wings are much rounded, and more or less of their body plumage loosely webbed. They subsist principally (and some of them it would appear wholly) on fruits; and, excepting the colies, are remarkable for the airy lightness of their movements.

The distinctions between the Rhamphastida and Musophagida, however, are considerably more obvious than their points of similitude, being principally external. The modification of the foot is very different, and in the former group, to which I shall now restrict myself, typically zygodactyle. From the singularity of their appearance, occasioned by the

At least, I can perceive no traces of such having been broken off, in the skeletons to which I have access.

disproportionate size of the bill, as compared with that of others of the feathered race, the Rhamphastidæ have excited a more than usual degree of interest; in consequence of which we are now in possession of much satisfactory information respecting their internal structure and economy. Some interesting details on their anatomy, by Prof. Owen, are appended to Mr. Gould's admirably illustrated monograph of the family; and the observations of several naturalists on their wild habits, together with those of Mr. Broderip, Mr. Vigors, and others, made upon individuals which have lived in captivity in Europe, leave little to be desired in order to complete our knowledge of their economy and general history.

I

On inspecting a fine perfect skeleton of a species of toucan (the only one which I have seen) in the Museum of Comparative Anatomy at Guy's Hospital, I found the entire structure to be less frail than descriptions had led me to anticipate; its conformation, however, evidently betokening a bird of feeble flight: the sternum was proportionally much larger than in the Musophagida, and similarly emarginated at its posterior edge; its crest low, though the pectoral muscles would seem to have been large and full, and LeVaillant expressly describes the toucans to have heavy and fleshy bodies, as is analogously the case with the diminutive todies. The separate clavicles were 13 inch in length, and taper at their extremities. These birds have a wide gullet, a moderately muscular stomach (which extends into the abdominal portion of the cavity of the body), no gall-bladder, the intestine short, not exceeding the length of the body, and devoid of cœcal appendages, as already noticed: they have been observed to regurgitate partially digested food, and after submitting it to a rude kind of mastication, again to swallow it: Petiver remarks the same of the syndactyle hornbills.

Exteriorly, their enormous bill has the first claim to our attention; the magnitude of which, in some instances, is indeed astonishing: this organ, however, is excessively and surprisingly light; its horny sheath being (save towards the tip) extremely thin, especially that of the upper mandible, but elastic, and though yielding in a slight degree to moderate pressure, presenting a considerable amount of resistance if the force be increased for the purpose of crushing the beak: its interior structure resembles what has been already described in the analogous instance of the hornbills. Its form is length

1 I take this opportunity to express my obligations to Mr. Gardiner, of the above-named institution, for the ready access which he has ever afforded me to the valuable collection of skeletons there deposited.

ened, and a little decurved, the downward bend increasing in both mandibles towards the tip: and its surface is extensively traversed by ramifications of the fifth pair of nerves, which render it unusually sensitive, in beautiful adaptation to the purposes for which it is employed. In connection with this sensitiveness, it may be remarked that these birds are careful to preserve their beak from cold, and at night are enabled to bury completely its immense bulk within their body-plumage: they are also frequently observed to scratch it gently with the foot, as if this produced an agreeable sensation. Its structure is extremely delicate in the young; and these, accordingly, must subsist on very delicate and soft food: and it is scarcely necessary to add that it does not attain its ultimate magnitude for a series of years; becoming finely coloured as it approaches to maturity. The edges of both mandibles are distinctly denticulated.

The tongue, as already noticed, is a very curious instrument, elongated and slender, and barbed not unlike a feather; its sheath giving off from the lateral margins a series of stiff bristle-like appendages, directed forwards, which structure is continued to the apex: the peculiar or accessory function of this sort of tongue appearing to be that of touch; it acting as a kind of antenna, whereby to test the softness and ripeness of fruit, and the fitness of other substances for food. That the toucans also possess, however, the sense of taste in very considerable perfection, will appear from a fact to be stated in the course of this summary: but the developement of nervous tissue and papille over the beak has been erroneously deemed an extension of the olfactory surface.

These birds have the legs of mean length, and covered, as are also the toes, with large scutelle: their feet are adapted for hopping from bough to bough. The wings are short and rounded; and tail of moderate length, and but slightly cuneated, in the genus Rhamphastos; longer, and much graduated, in the others: it is mostly held erected. The cheeks are bare; the skin of them being generally blue, and sometimes red, or even green: irides most commonly pale blue: and the clothing plumage is of rather open texture (as in the motmots), having the webs of the feathers disunited, and often glistening on those parts that are brightly coloured:1 the accessory plume is flocculent and of considerable length, in some,

1 One species, known as the curl-crested aricari, is remarkable for a curious modification of the feathers of its crown, which have the webs soldered so as to be undistinguishable, appearing like curled and brilliantly shining lamine of black sealing-wax. The intent remains to be explained.

but reduced to a mere tuft in others. They are birds of gorgeous colouring, and peculiar in the disposition of their tints: the true toucans being chiefly black, with large masses of crimson, white, or yellow (or very rarely faint blue), on the breast or below, and especially beneath the tail, where it is rendered conspicuous by the habitual elevation of the latter; there is often, also, a band of bright colouring across the rump, and generally a gorget of one or more different hues contrasting with and bounding the mass of colouring on the forepart of the breast the aricaris differ in having the upper parts chiefly green, of various degrees of brightness, and are in general rather more variegated: in these the sexes also differ, the female being chestnut-rufous where the male is black; whereas the male and female toucan present only a trivial disparity of size: the groovebills (Aulacorhynchus, Gould), which constitute a sub-genus of aricaris, have the ground colour vivid green. In all the young possess the gorgeous livery of the adult, and are at first sight chiefly distinguishable by their smaller beaks. Azara remarks, that he has often observed that these, when brought up tame, underwent a moult when about two or three months old: at which time there can be little doubt, from analogy, that the primaries are shed. Levaillant and others have considered the relation which the aricaris bear to the toucans, to be similar to that which the magpies and jays hold to the crows and ravens.

These birds breed in the hollows of decayed trees, producing (in every known instance) two delicately white eggs, of a nearly spherical form: the young recurve their tails upon the back while in the nest. They are of a social disposition, small flocks of ten or a dozen being commonly seen together; different species of them mingling in society. They are shy of approach, more particularly the larger toucans which generally perch on the higher branches of lofty trees, where they skip from bough to bough with the most lightsome agility; or sit, with invariably the beak turned towards the wind. They fly rapidly, but evidently with much exertion, and with difficulty against the wind; at a mean height, and always in a straight line; flapping their wings at intervals, and with some noise; and carrying the beak elevated above the level of the body, with the tail overlying the back. On the ground they are rarely seen, where they advance by oblique hops, and rather awkwardly. They are very fond of washing. Individuals are often noticed perched upon high trees, watching the moment at which other birds leave their nests, on which they instantly pounce to feed on the eggs or young, sometimes even contesting a prize with the monkeys. The ex