CLASSIFICATION 87 



undue dogmatism ; and besides, it must be inaccurate, as it is not in 

 three dimensions. A given naturalist may have strong reasons for 

 believing, let us say, that the Struthious birds represent the lowest bird 

 stock, from which arose in a regular series of branches, indepen- 

 dently, and alternately from one side or the other, the various groups 

 into which we divide the class in the present book ; if so, then the 

 Stammbaum is easily constructed. But the general consensus of 

 opinion is that the inter-relationships of the different groups cannot 

 be expressed with so much simplicity. It is clear that, in any case, 

 the most modified offshoots must occupy the highest branches of 

 the tree, and that we may in a linear scheme conveniently begin or 

 end with them. But it is impossible to arbitrate as to which group 

 is the most specialised. It is, on the whole, agreed that the Ostrich 

 tribe have retained more primitive characters than other birds ; but 

 is the elaborate voice-mechanism of the Nightingale, or the almost 

 human intelligence of the Haven or Parrot, to rank first as evidence 

 of high position, i.e. specialisation, remoteness from the original 

 stock ? This is a matter about which everybody can legitimately 

 have an opinion ; and we cannot at present formulate a creed for 

 those, that is to say, who are acquainted with the facts. 



The scheme that I adopt here is the same as that which Mr. 

 Hudson uses in the pages which follow ; it is the plan followed in 

 the B.O.U. list, and approved by most ornithologists in this country 

 as a convenient working outline. I have added to it the fossil 

 groups, and those groups which do not occur in Great Britain. The 

 main scheme is that of Dr. Gadow, used in his valuable account of 

 the anatomy of birds in Bronn's ' Klassen und Ordnungen des 

 Thierreichs.' There is no deep-seated and mysterious reason for 

 my placing Parrots at the end of the Aves Carinatae : it is simply 

 sheer inability to place them anywhere in particular. 



CLASS. AVES. 



SUB-CLASS I. Archaeornithes (contains genus Archseopteryx only). 

 SUB-CLASS II. Neornithes. 



Division i. Neornithes Batitse. 



Order i. Katitse (contains Struthio, Ehea, Dinornis, &c.). 

 Order ii. Stereornithes (contains a few fossil genera, Gast- 



ornis, Dasornis, &c.). 

 Division ii. Neornithes Odontolc. 



Order i. Hesperornithes (the extinct Hesperornis and 

 Enaliornis). 



