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Show 1882.] ()N THE ANATOMV OF PASSERINE BIRDS. 569 tures in its dorsal wall, and give off branches to the outer face the lung, representing the ectobronchial system of birds. The orifices with which the surfaces of all these canals, except the auterior half of the mesobronchium, are thickly set, lead into depressions, which are often so deep as to become cylindrical passages, simulatiug the parabronchia of birds. Thus, notwithstanding all the points of difference, there is a fundamental resemblance between the respiratory organs of Birds and those of Crocodiles, pointing to some common form (doubtless exemplified by some of the extinct Diuosauria), of which both are modifications. 3. Contributions to the Anatomy of Passerine Birds.-Part VI.1 O n Xenicus and Acanthisitta as types of a new Family (Xenicida) of Mesomyodian Passeres from N ew Zealand. By W . A. F O R B E S , B.A., Fellow of St. John's College, Cambridge, Prosector to tbe Society. [Received June 19, 1882.] A few months ago I received, through the kindness of my friend Prof. Jeffrey Parker, of the University of Otago, New Zealand, a small collection of birds in spirit from that country, which included most of the peculiar forms of Passeres found there. Amongst them were single specimens of Xenicus longipes and Acanthisitta chloi'is, the examination of which has proved to be of especial interest. The genus Xenicus was founded by the late Mr. G. R. Gray 2 for the reception of the Motacilla longipes of Gmelin3, Lafresnaye having some twenty years previously established Acanthisitta for Sparrman's Sitta chloris4. Subsequent ornithological writers have pretty unanimously assigned both these forms to the " Certhiidae " or their immediate neighbourhood, in company with Sitta, Sittella, and their allies. The peculiar structure of the tarsus in Xenicus first induced me to examine these birds more closely, with the unexpected result that I find that the two genera in question are true Mesomyodian forms, and therefore in no intimate degree related to such Oscines as those just mentioned. The subjoined drawings of the syrinx of Xenicus-with which in all points Acanthisitta appears to agree in every essential respect- will show that it has none of the complex nature of that organ in the Oscines, the thin lateral tracheal muscle terminating on the upper edge of a somewhat osseous box formed by the consolidation of the last few tracheal rings, and there being no other intrinsic 1 For Part V. vide antea, p. 544. 3 Rev. Mag. Zool. 1842, Ois. pl. xxv 2 Ibis, 1862, p. 218. 4 Mus. Oarls. fasc. 2, no. 33. 38* |
