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Show 146 ON THK ANATOMY OF THE CONDOR. [Mar. 18, The additional muscular and tendinous slips which have been described in this paper as uniting the valve-margin with the parietes in certain birds are comparable to the additional muscles which tie down the valve in the Monotremata, and, as has been pointed out, they are traceable in the Crocodile heart. 2. Trachea. The trachea of the American Vultures (including, of course Sar-corhamphus) has been long known to differ greatly from that of other Accipitres in having no intrinsic muscles, and in showing no definite modification in the direction of the formation of a syrinx. a-, oesophagus; m, muscles enveloping extremity of bronchia; Tr, trachea; o, ostia ; s, septum dividing prebronchial from anterior intermediate air-sac ; sp, septum between anterior and posterior intermediate air-sac. In all three genera the bifurcation of the trachea is very similar but on the whole Sarcorhamphus comes nearer to Gypagus than either of them do to Cathartes. This is principally shown in the comparative thickness of the rings at the point of bifurcation ; these are extraordinarily thin in Cathartes, leaving therefore large membranous spaces. The bifurcation of the trachea in Cathartes is especially Lacertilian. The rings of the bronchi in Sarcorhamphus cease for some time before the bronchi enter the lungs; this fibrous portion (see woodcut fig. 3) is closely enveloped by a mass of muscle (m). The function of this muscle must be much the same as that of the intrinsic muscles of the syrinx in those forms which are furnished with |