OCR Text |
Show 1885.] MR. F. E. BEDDARD ON THE CUCKOOS. 185 detail, but agree in the main fact that the pectoral tract is single and not bifurcate. Cacomantis and Cuculus are in some respects different from the three other genera, as might indeed be expected from their different geographical range ; they resemble each other in the peculiar arrangement of the ventral tract, which in its posterior portion at the end of the sternum is composed of three rows of feathers, of which the outer one, as shown in the accompanying drawing (fig. 3, p. 175), bends outward at some distance from the inner rows but approaches them before its termination. The three American genera Piaya, Saurothera, and Coccyzus agree to differ from the Old-World representatives of this group, in that the ventral tract is double from the point of origin at the mandibular symphysis ; in Cuculus and Cacomantis the commencement of the ventral tract occupies the whole, or nearly the whole, of the area lying between the two mandibular rami, and is single. Group B includes the genera Centropus, Pyrrhocentor, Geococcyx, Guira, Crotophaga, Phcenicophaes (Rhinococcyx), and Eudynamis. Phcenicophaes, although regarded by Nitzsch as differing in important particulars from Centropus and Eudynamis, does not appear to me to display any such peculiarities in its pterylosis as would necessitate a further division of this group; it has been stated, however, that both Phcenicophaes and Eudynamis, although agreeing with the other genera of this group in their pterylosis, resemble Cuculus in possessing a tracheo-bronchial syrinx, and on this account should be placed apart. The remaining genera of this group may be arranged in two divisions :- (1) Crotophaga, Guira, and Geococcyx, where the ventral tract is narrow at its commencement, and only occupies the median portion of the intermandibular area. (2) Centropus and Pyrrhocentor, where the ventral tract at its commencement occupies the whole of the space between the rami of the mandibles. It will be observed that this arrangement conveniently separates the New-World from the Old-World genera, though the distinction is undoubtedly a very small one ; perhaps the resemblance between Geoccocyx aiid Centropus in the matter of the syrinx should be made more account of, and these genera separated from Crotophaga and Guira. Recalling the structure of the syrinx in the several genera, it will be apparent that group A is also distinguishable from group B by means of the structure of this organ. In all the genera which I have associated together in the former of these two groups, the syrinx is tracheobronchial; in Group B, with the exception of the genera Eudynamis and Phcenicophaes, the syrinx is brouchial, though by no means constructed on exactly the same type in the different genera; in Crotophaga and Guira the syrinx is purely bronchial, inasmuch as the anterior rings of the bronchi are complete, and the membrana tympaniformis does not therefore extend up to' the last tracheal ring ; and there can be no pessulus, and the tracheal rin«-s therefore take no share in the formation of the voice- |