

VERTEBRATA : AVES. 595 



cated to be available for the general student, and therefore to 

 be useful in a work of the present nature ; but it is intended 

 primarily for the anatomist, and not for the systematic zoolo- 

 gist. The latter requires a classification based upon all the 

 characters, internal and external ; whereas the morphological 

 method of arrangement selects simply single structures in the 

 anatomy of the bird, and fixes its place by means of these. 

 Thus, Prof. Huxley founds his classification of the Carinatcz 

 upon the structure of the bony palate. This method of classi- 

 fication, however, though of the greatest use to the compara- 

 tive anatomist, cannot be made to coincide with any purely 

 zoological mode of arrangement. It has, therefore, seemed 

 preferable for the purpose of the present work to adhere, with 

 some modifications, to the old classification of Birds, which is 

 to be found, in one form or another, in almost all the'Standard 

 works on ornithology. In using, however, the six old orders 

 of this system, with their familiar and long current names, the 

 student must remember that they bear very unequal values. 

 Some of them such as the Natatores, Grallatores, Rasores, 

 and Raptores are essentially natural groups, and cannot be 

 seriously mutilated in any system of classification. The order 

 Insessores is also, in the main, a natural one, though it in- 

 cludes groups which can only be artificially connected with it. 

 On the other hand, the order Scansores is a conspicuously 

 unnatural one, and is retained here simply as a matter of 

 convenience. 



SUB-CLASS I. RATITVE. 



ORDER CURSORES. The first order of Birds is that of 

 the Cur sores, or Runners, comprising the Ostriches, Rheas, 

 Cassowaries, Emeus, and the singular Apteryx of New Zealand. 

 The Cur sores are characterised by the rudimentary condition of 

 the wings, which are so short as to be useless for flight, and by 

 the compensating length and strength of the legs. In accordance 

 with this condition of the limbs, many of the bones retain 

 their marrow, and the sternum (fig. 329, A) is destitute of the 

 prominent ridge or keel, to which the great pectoral muscles are 

 attached (hence the name of Ratitcz, applied by Huxley to the 

 order). In the Ostrich, the pubic bones of the pelvis unite to 

 form a symphysis pubis, as they do in no other bird ; and in 

 all, the pelvic arch possesses unusual strength and stability. 

 The legs are extremely robust and powerful, and the hind-toe is 

 entirely wanting, except in the Apteryx, in which it is rudimen- 

 tary. The anterior toes are two or three in number, and are 



