THE CLASSIFICATION OF BIRDS 161 



of birds have, so to speak, been distributed with such exceed- 

 ing fairness through the class that no type has any great 

 advantage over its fellows. PARKER has collected together 

 some of the reptilian survivals, and to his series a few others 

 may be added. The rudimentary organ of Jacobson found 

 by T. J. PARKER in Apteryx is a suggestion of the reptile ; 

 but we do not know enough about the development of other 

 birds (except the struthious, where PARKER found the same 

 rudiments himself) to lay much weight upon the discovery 

 as indicative of the low position of Apteryx in the avian 

 system. The supra-orbital chain of bones is also on the 

 same grounds an archaic character ; but they exist in 

 such widely different types as tinamous, Psophia, Menura, 

 and quails. The double vomer is reptilian ; this bone is 

 double or nearly so in struthious birds, in Hcsperornis, 

 woodpeckers, and even in passerines and other types with a 

 broad vomer. PARKER has compared the ' os uncinatum ' 

 with the anterior suspensory cartilage of the tadpole's jaw 

 apparatus ; this is found in so many and such various forms 

 as Cariama, Fregata, Tubinares, Musophagida?, Steatornis, 

 &c. Basipterygoid processes are distinctly reptilian, found 

 as they are in so many forms of reptiles. But among birds 

 they occur in nearly every big group, and are therefore most 

 undistinctive. The pectineal process, if it is invariably as 

 T. J. PARKER says it is in Apteryx the joint product of pubis 

 and ilium, is not exactly comparable to the supposed corre- 

 sponding process of the dinosaurian pelvis ; but in any case it is 

 found in Geococcyx and some other birds far away from the 

 Struthiones and the tinamous. A large number of vertebrae 

 in the tail is reptilian ; but not only Arcliceopteryx but also 

 the swan has a long tail. Opisthocoelous vertebrae are 

 found in the Alcse, penguins, and gulls, not to mention the 

 darters and parrots. 



As to the viscera, HUXLEY showed the close likeness be- 

 tween the various membranes which divide the coelom and the 

 corresponding membranes in the crocodile, and I endeavoured 

 to show that the ostrich is not in these particulars more 

 reptilian than many other birds. The partial persistence 



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