64 NATURAL SCIENCE. Jan.. 



Charadiiformes ; and the Coraciomorphae, the CucuHformes, Coracii- 

 formes, and Passeriformes. 



Such are the main divisions of Dr. Gadow's scheme. To pursue 

 it further, would be neither permissible nor desirable here ; but we 

 think, in justice to our task, we should indicate some of the principal 

 features of the remainder of the book ; which, as we have previously 

 hinted, is simply teeming with information, not of the " handy 

 reference-book " order, but facts, skilfully marshalled. 



Dr. Gadow commences with a short definition of the Class Aves, 

 in which he admits the derivation of birds from reptiles; though from 

 which sub-class cannot of course be proved. We are reminded that 

 the distinction between birds and " not-birds " is unmistakable; yet 

 it is only a question of time for some fortunate palaeontologist to bridge 

 over the gap, since gap there must be, for such remarkable structures 

 as feathers, and the modification of the fore-limb into the characteristic 

 Avian wing, cannot have come suddenly into existence. Archaop- 

 teryx, the most archaic bird we know, has attained a high degree 

 of development ; so that there must have existed a long chain of 

 unknown forms connecting it with the reptiles. For such inter- 

 mediate forms the term " Herpetornithes " is proposed. 



The Neornithes are probably the direct descendants of the 

 Archaeornithes ; but whether Avchcvoptetyx was a direct ancestor, or 

 only a small side branch, is a matter for speculation. The Neornithes 

 seem to have become well developed by the end of the Jurassic 

 period ; in Cretaceous times they still retained teeth, but had even 

 then developed into flying forms with a pygostyle, and flightless forms 

 without either a carina sterni or pygostyle. 



After discussing the characters, whether primitive or pseudo- 

 primitive, which distinguish the Ratitae from the remaining birds, 

 Dr. Gadow proceeds at some length to dilate upon the relation of the 

 Ratitae to the Carinatae. He opens his argument by very properly 

 disposing of the mythical relationship, hitherto considered by some to 

 exist between the Ratitae and the Dinosaurs on the one hand, and the 

 Carinatae and Pterosaurs- — through Arcliiropteryx — on the other, as 

 "profitless dreaming"; pointing out that, if the similarity of the 

 hind-limb existing between certain of these reptiles (the Dinosaurs) 

 and the Ratitae be held to be a proof of relationship, then all birds 

 must be derived from the same stock, since in all birds the component 

 elements of the tarsus are the same. Proceeding, the author next 

 discusses the mono- or polyphyletic derivation of the Ratitae, and this 

 section will require very careful reading. Dr. Gadow's conclusions 

 have led him to regard the Ratitae as monophyletic. He proposes 

 to retain the " Ratitae " as a separate group, " upon practical 

 taxonomic grounds." 



The division " Neornithes Odontolcae " appears to have been 

 made with some diffidence to contain the Hesperornithes and Enalior- 

 nithes ; but, it is urged, the arrangement must remain until Jurassic or 

 Cretaceous birds are discovered, which possess a carina sterni and 

 teeth standing in a groove. 



The third and last division — "Neornithes Carinatae" — contains 

 all the remaining birds. Of brigade i it is noteworthy that the 

 Colymbomorphae (= legion i) include the Ichthyornithes — and, we 

 presume, but for special reasons, the Hesperornithes would have been 

 included also. Passing on to the Coraciomorphae, for space will not 

 permit us to slowly meander as we should wish through the inter- 

 mediate groups, we notice that the author confirms his earlier paper 



