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Show 390 MR. W. A. FORBES ON T H E [May 4, a second, though shallower, fenestra is formed between them and the second and third pairs. The fifth semirings are slightly dilated at their extremities, where they are in close proximity, before and behind, with the first four pairs. The sixth and succeeding bronchial rings take on the ordinary character, being deeper than those that precede them, and gradually becoming more complete, till the fifteenth pair are nearly perfect. O n one side, the left, in this specimen, the eighth and ninth semirings are partially fused externally. The lateral muscles of the trachea, after the insertion of the stemo-tracheales, become excessively thin, so that it is difficult to make out accurately their exact extent. They apparently fan out, so as to be nearly in contact with each other before and behind, and are inserted onto the first bronchial semirings for the greater part (as far as I can make out) of their lateral surface, the tips, however, being quite free from muscular fibres. Philepitta is therefore perfectly Mesomyodian, as Prof. Garrod predicted would probably be the case'. There are thus three families of Mesomyodian Passeres in the Old World-the Pittidce, the Philepittidee, and the Euryleemidee. All agree in the possession of a broncho-tracheal syrinx, in that respect agreeing with the Cotingidee (including Rupicola), Pipridee, and Tyrannidee of the New World, and differing from the Tracheophone families, which are all, as is well known, American. Philepitta differs in the details of its syrinx from all the other " Haploophone " Passeres. In Pitta (cf. P.Z.S. 1876, pl. 53. figs 1-6) the bronchial semirings are much less modified, being nearly entirely simple semirings ; the lateral muscle, too, is slender and not spread out as in Philepitta. This fact, taken with others, as the scutellation of the tarsi, osteology, & c , justifies, in m y mind, the establishment, as has been done by Sundevall under the name Paictidee, of a separate family for the bird under consideration 2. The Euryleemidee differ in their retention of a plantar vinculum (cf. Garrod, P.Z.S. 1877, and supra, p. 382), as well as in the structure of their feet and other points. In the form of their syrinx, however, they approach Philepitta perhaps more nearly than any form yet described, though in them too the lateral muscle remains slender and unexpanded. The peculiarities of the Euryleemidee, and especially their oft-spoken-of retention of the plantar vinculum, are sufficient, I think, to justify their forming a main division of Passeres by themselves, as suggested by Prof. Garrod 3, which may be termed D E S M O D A C T Y L I in distinction from the others or E L E U T H E R O D A C T Y L I . Prof. Garrod's arrangement of Passeres4 may therefore be modified as follows :- 1 Voice-organs of Passeres, p. 68. 2 The general myology and vascular system of Philepitta are still, it must be remembered, unknown, but are in all probability perfectly Passerine. 3 Voice-organs of Passeres, p. 73 and P. Z. S. 1877, p 449. 4 P. Z. S. 1876, p. 518. |
