. La structure et la classification des oiseaux . ardly mérite le nom. Dans la tribu de stok, nous avons une série d'étapes dans la dégénérationdu syrinx. Chez Abdvmia sphenorhyncha, comme chez les autres orkstans, il n'y a pas de muscles syringés intrinsèques, mais themembrana tympaniformis est bien développé et de portée à considérer. Chez Xenorhynchus, les membrua tympaniformisis sont presque, mais pas tout à fait, oblitérés, et, enfin, chez Ciconiathe, les cernes bronchiques sont des anneaux, et non des demi-anneaux ; il n'y a pas de trace d'un membrua tympaniformis ; mais dans toute la structure F ET LA CLASSIFICATION DES OISEAUX pessulus est présent

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. The structure and classification of birds . ardly deserves the name. Inthe stork tribe we have a series of stages in the degenerationof the syrinx. In Abdvmia sphenorhyncha, as in otherstorks, there are no intrinsic syringeal muscles, but themembrana tympaniformis is well developed and of consider-able extent. In Xenorhynchus the membrana tympaniformisis almost, but not quite, obliterated, and, finally, in Ciconiathe bronchial rings are rings, and not semi-rings ; there is inthem no trace of a membrana tympaniformis ; but in all the F STRUCTURE AND CLASSIFICATION OF BIRDS pessulus is present. The syrinx of the stork, indeed, and ofthe American vultures very nearly approaches what weshould on a priori grounds regard as the original form ofthe syrinx. In the other direction the syrinx may be further increasedin complication; this is brought about by an hypertrophy ofthe intrinsic muscles. The simplest case is that of theplover, Vanellus cayennensis, figured and described byGabrod, whose figure is here reproduced. It will not need. Fig. 45.—Sykinx of Vanella cayennensis, fkom in feont (aftee Gaeeod). much description; the principal change is in the enormouslythickened pair of muscles. This modification of the syrinx, however, is seen at itsextreme in certain passerines and in the parrots. Here wemeet with a multiplication of the intrinsic muscles, whichmay exist to the number of three or four pairs. A syrinx ofthis kind, when found in the Passeres, is frequently termedoscinine, the group of Passeres exhibiting the character beingthe Oscines, a term, however, which is not now used in theclassification of the group. On the Trachea of the Tantalus loculatc& and of VaMellus cayennensis, P. Z. 8. 1878, p. 625. RESPIRATOEy SYSTEM 67 In Menura superba, which has been described by GarKod., there are three, pairs of muscles, which are attached todifferent bronchial semi-rings; the posterior pair of musclesare attached to a ring below that which bears the insertionof the anter

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• bookcentury1800
• bookdecade1890
• booksubjectbirds
• bookyear1898