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Show 1885.] VISCERAL ANATOMY OF BIRDS. 837 down the barriers between the Ratitae and the Carinatse in the first these two directions, I may briefly review our knowledge upon the subject. In his classical paper upon the ' Classification of Birds'1 Prof. Huxley defined the Ratitae, and pointed out the differences which separate them from the Carinatee. Although that paper was only published in the year 1867, it is interesting to note how the progress of research has broken down so many of the barriers which at that time were supposed to separate the Ratitae from the Carinatae. The peculiarities of the skull I need not refer to, since they are repeated in the Tinamous, which in so many other respects resemble the Gallinaceous birds, and therefore form an annectent group between the Ostrich-tribe and the other Carinatae. The shoulder-girdle has been held to be characteristic and to form a well marked distinction between the Ratitae and the Carinatae ; but anatomists are now agreed that tbe sternum, at least, is not so characteristic as it was at one time believed to be. In the first place the presence of a " keel" is invariably associated with the power of flight, or, to speak more accurately, with a great development of the pectoral muscles; thus we find a keel on the sternum of the Bat, Mole, and P^erodactyles, while it is absent in Strigops, the flightless parrot of New Zealand, and in Cnerniornis2. Moreover, Prof. Jeffery Parker, in a paper upon the Osteology of the New Zealand Rails3, has given reasons for believing that the angle between the scapula and the coracoid becomes less and less as the power of flight is diminished, so that this supposed peculiarity in the shoulder-girdle of the Struthiones is merely correlated with the loss of the power of flight. It is commonly stated that the Struthiones possess no lower larynx, and this assertion is repeated from text-book to text-book in spite of the fact that m y predecessor, the late Mr. W . A. Forbes, has conclusively shown4 that certain of the Struthiones, if not the whole group, possess a syrinx which is essentially comparable to the syrinx of the Carinatse, and, in the case of Bhea, is absolutely indistinguishable from a Carinate syrinx. Certain of the statements of Sir Richard Owen respecting the anatomy of Apteryx have been since controverted. Prof. Huxley has shown that the respiratory organs of this bird, though certainly differing in detail, present no essential modifications from the respiratory organs of other birds ; there is no structure unrepresented in other birds present ; the supposed "diaphragm" is in reality not comparable to the diaphragm of the mammalia; and even if it were, it has its exact homologue in the Carinata?. Prof. Lankester 5 and 16 have shown that the heart of Apteryx is precisely like that of any other bird. The presence of two nails upon the hand of Struthio, to which Prof. Huxley has called attention, is no doubt, so far, an archaic 1 P. Z. S. 1867, p. 415. 4 Collected Papers, p. 232. 2 See P. Z. S. 1873, p. 763. 5 P. Z. S. 1885, p. 415. 3 Trans. N.-Z. Inst. vol. xiv. p. 245. 6 P. Z. S. 1885, pp. 188, 477 |