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colour ; thus three desert forms of the Chukar Partridge have been described by Mr. Hume as 

 distinct species, under the names of Caccabis pallidus, C. pallescens, and G. arenarius, none of 

 which appear to me to be worthy of specific rank. American ornithologists have of late adopted 

 the plan of designating such by means of trinomial appellations, and would call these three 

 forms Caccabis chukar pallidus, Caccabis chukar pallescens, and Caccabis chukar arenarius ; 

 but this appears to me a highly objectionable retrograde step, as it will only tend to make 

 the study of ornithology more difficult instead of simplifying matters. 



It will be necessary to make a few remarks relative to the classification I have adopted in 

 the present work, especially as I have departed from that which has hitherto been so universally 

 employed by authors who have written on European ornithology. Recent research has shown 

 that the old Cuvierian system of classification, in which the Eaptores head the list, cannot stand ; 

 and it is universally conceded that a fresh classification is absolutely necessary. Having carefully 

 considered the matter, I came to the conclusion that Professor Huxley's classification of birds 

 is undoubtedly the best in principle, especially as it is the one which anatomists agree in 

 adopting ; I have therefore made use of it, though in so doing I have, as will be seen, adopted 

 his principle rather than his practice, and have accepted the modifications which have been 

 suggested since his first paper on the subject, and more especially those proposed by Mr. Sclater, 

 who appears to have been the first to make practical use of Professor Huxley's system, and has 

 done much to popularize it. An article recently published by him (Ibis, 1880, pp. 340-350, 

 and 399-411) gives the outlines of this classification of birds ; and I may refer such of my 

 readers as may wish for further details respecting the same to it. The basis of this system of 

 classification was first proposed by Professor Huxley in 1867 (P. Z. S. 1867, pp. 415-472), in 

 a paper " On the Classification of Birds ; and on the Taxonomic Value of the Modifications of 

 certain of the Cranial Bones observable in that Class." In this paper he points out that birds 

 are so nearly allied to reptiles in all the essential and fundamental points of their structure that 

 to associate them into one primary group of the Vertebrata, the Sauropsida, as formerly proposed 

 by him, is a necessity ; and in proof of this he enumerates the principal points in which Aves 

 and Reptilia agree with one another and differ from the Mammalia. Having arrived at the 

 conclusion that the class Aves, while well enough defined from all existing Reptilia, is more 

 closely connected with this class than with any other, he proceeds to divide it into three 

 or d ers — the Saururse, the Ratitse, and the Carinatse. The first of these is represented by the 

 solitary fossil Archwopteryx, and has no representative at present in existence ; the second class, 

 the Ratitee, contains the Struthious birds, which have no keel developed on the sternum ; and the 

 third class embraces all existing birds except the Ratitse, which have the sternum keeled, and 

 ossified from a median centre in that keel, as well as from lateral paired centres. Of these 

 three classes the Carinatee alone are represented in Europe ; and therefore with them only are 

 we concerned. These birds are divided by Professor Huxley into four suborders, according to 

 the peculiarities in the arrangement of the palatal bones, as these characters, being independent 

 vol. i. c 



