one. b. Ventral tract only occupying median region. Geococcyx New World. The question of the affinities of the cuckoos is a difficult. By GADOW they are placed nearest to the Musophagi and next nearest to the Psittaci. FÜRBRINGER'S views do not greatly differ. There seems to be no doubt that these birds. are an archaic group not far from the point where the Anomalogonatæ and Homalogonatæ of GARROD diverge. They are, like the Musophagi, quintocubital; their intestines are simple; and they have the complete muscle formula (B being in some forms absent). These characters are found in others among the more primitive of the higher birds. The likenesses which the cuckoos show to the Pico-Passeres are mainly in the structure of the foot, in the simple character of the tendons of the patagium, and the marked resemblance in the syrinx to that of the Caprimulgi, and in a less degree to the Striges. As has been pointed out, precisely the same series of modifications between the extreme bronchial syrinx of Crotophaga and the purely tracheo-bronchial syrinx of Cuculus are to be seen among the Caprimulgi. The syrinx is really the only salient point in the anatomy of the group that can be laid hold of for purposes of comparison, and, considering the dissimilarities in the voice and habits of cuckoos and goatsuckers, it is particularly noteworthy. As to fossil cuckoos, the two most interesting facts are, perhaps, the occurrence of Centropus and Phonicophaes1 in See MILNE-EDWARDS in Comptes Rendus for 1894. Europe, especially the latter, as it has some claims to represent the most ancient form of cuckoo, with complete muscle formula and tracheo-bronchial syrinx.' MUSOPHAGI Definition.-Oil gland tufted. Aftershaft present. Quintocubital. Rectrices, ten. Muscle formula of leg, ABXY+. Expansor secundariorum present. Biceps slip absent. Cæca absent. Both carotids present. Skull holorhinal, desmognathous, without basipterygoid processes. This group of birds, purely African in range,' is divisible into three genera, Corythaix, Musophaga, and Schizorhis. These genera do not show a large amount of structural variation. As to the pterylosis, the two ventral tracts are double upon the neck (in C. albocristata); they remain separate until just in front of the cloaca, being especially weak and narrow in the breast region. Longitudinally arranged rows of feathers connect the pectoral tracts above with the humeral. The other important external characters are stated in the definition. In Schizorhis the normal arrangement of the leg arteries obtains. In Corythaix and Musophaga the femoral artery is the one developed. The right jugular is the largest, and in Corythaix albocristata seems to have entirely disappeared. In the liver the right lobe is the larger, sometimes considerably so. The gall bladder is present, and sometimes is elongated in form. The tongue is short and triangular; the proventriculus is zonary, the gizzard weak. The intestines are capacious and short, without cæca. The following are a few measurements: Cf. also partial persistence of basipterygoid processes in Phoenicophainæ. 2 The extinct Necrornis of French Miocene may be a Touraco. 3 The viscera are described by OWEN for Corythaix porphyreolopha, P. Z. S 1834, p. 3, and by MARTIN for Corythaix Buffonii, ibid. 1836, p. 32. The windpipe of Corythaix persa is slightly swollen along its course, narrowing again at the bifurcation. It is much ossified. Counting as the last tracheal ring that to which the pessulus is attached in front, the intrinsic muscles are inserted on to the third in front of this. The first two bronchial semi-rings are ossified; the third, between which and the second there is a considerable membranous interval, is the first of the purely cartilaginous series. The extrinsic muscles stout, and arise seven or eight rings from the end of the trachea, and pass at once to their insertion; they run no distance along the trachea, as is so common. are FIG. 139.-INTESTINES OF Corythaix Musophaga has no intrinsic muscles; Schizorhis has. As to muscles, the tensores patagii are very simple, and the biceps slip is entirely absent. The tensor brevis sends off a wristward slip just before its insertion in both Musophaga and Corythaix; it is reinforced by a pectoral slip and by a fibrous slip from the humeral crest. The anconaus longus has not, at any rate in Corythaix albocristata, a humeral head. Glutaus I. is large, covering the biceps; glutæus V. is absent (Corythaix erythrolophus, Musophaga) or present (Schizorhis africanus). The muscle 'Absent-perhaps as an individual variation-in C. albocristata. formula of the leg, as stated in the definition, is ABXY+. Both peroneals are present. The deep flexor tendons are bound by a vinculum, which is single in Corythair and double in Schizorhis. The skull of Corythaix is barely desmognathous, and by no manner of means especially like that of a cuckoo, to which group the Musophagi have been often compared. The hinge in the middle of the face is nearly complete, but there is a bridge on each side, formed by an ankylosis between the frontal and nasal. The holorhinal nostrils are situated very far forwards, and each has, as PARKER' has pointed out, an osseous fold upon the ossified internarial septum. The maxillo-palatines diverge from each other posteriorly for a much longer space than in any cuckoo. The ascending laminæ of the palatines come into contact for a very brief space over the rostrum in front, and are continued forward for a short distance as a sharp spike. Between them lies a minute interpalatine splint (or vomer). The interorbital septum is moderately fenestrate. The lacrymal bones are of some size, and the descending process is closely applied to, but does not fuse with, the square ectethmoid process; connected with both is a small os uncinatum, which reaches the palatine.2 In view of the general opinion as to the nearness of the In his paper upon Opisthocomus. See below, p. 286, footnote. 2 J. T. REINHARDT, Vid. Medd. Kjöbenhavn, 1871, p. 326. alliance between Musophagidae and Cuculidæ it may be useful to tabulate the principal divergences in the skull. Corythaix has 14 cervical vertebra; the atlas is notched, not perforated by the odontoid process. Four ribs reach the sternum, which is doubly notched and has a strong spina externa. In the pelvis the prepubic process is very markedly developed, as in Geococcyx. The clavicle comes into contact both with the scapula and with the moderately large procoracoid; the latter is fused with the acrocoracoid, making thus a complete bridge over the sulcus supracoracoideus. The coracoids slightly overlap at their articulation with the sternum. The hæmapophyses are characteristic. In Corythaix albocristata C11 has paired processes; on C12 and C13 the hæmapophyses form a continuous ventral keel to those vertebræ. The three following vertebræ have hæmapophyses. The extremities of those of D1 and D2 are expanded with a median ridge, owing to the catapophyses having descended them.3 OPISTHOCOMI Definition. Aftershaft present. Oil gland feathered. Rectrices, ten. Quintocubital Muscle formula, ABXY+. Biceps slip and expansor secundariorum present. Carotids, two. Ceca present. Skull holorhinal, schizognathous, without basipterygoid processes. Sternum peculiar in form, wider behind than in front; the spina externa ankylosed with furcula. There is no doubt that this group, consisting of but a single genus and species, Opisthocomus cristatus, the hoatzin of British Guiana, forms a well-marked group of birds. The external characters of the adult and young have been chiefly described in recent years by NITZSCH, PYCRAFT,1 and In Corythaix persa the atlas ring is incomplete. 2 Cf. Galli, in which the same fusion occurs. 3 E. BLANCHARD, Remarques sur l'Ostéologie des Musophagides,' Compt. Rend. xlv. p. 599. On the Pterylography of the Hoatzin,' Ibis, 1895, p. 345. |