DINOSAURS. 109 



class, the possibility and even probability of birds and Dinosaurs 

 being descended from a common ancestor is a theory for which 

 much may be said, and it has been adopted by many leading 

 naturalists ot the present day, who have been convinced by 

 Professor Huxley's clear elucidation of the nature of the pelvic 

 region in the group of Dinosaurs which has been above described 

 (the Ornithopoda, or bird-footed group). It was Professor 

 Huxley who first propounded this interesting speculation, 

 basing his belief on the many bird-like characters presented by 

 this strange group of extinct reptiles the small head and fore 

 limbs, the long and often three-toed hollow hind limbs, the bones 

 of the pelvis or haunch, their habit of walking in a semi-erect 

 position on those limbs (as proved by their tracks), and in some 

 of hopping, as the little Compsgnathus most probably did. And, 

 last but not least, the strange mixture of bird-like and reptilian 

 characters presented by certain most anomalous birds dis- 

 covered by Professor Marsh in American Cretaceous rocks, viz. 

 the huge Hesperornis and the smaller Ichthyornis. Speaking 

 on this subject some years ago, Professor Marsh said, " It is now 

 generally admitted by biologists who have made a study of 

 vertebrates, that birds have come down to us through the 

 Dinosaurs, and the close affinity of the latter with recent struthious 

 birds (ostrich, etc.), will hardly be questioned. The case amounts 

 almost to a demonstration, if we compare with Dinosaurs their 

 contemporaries, the Mesozoic birds. The classes of birds and 

 reptiles, as now living, are separated by a gulf so profound that a 

 few years since it was cited by the opponents of Evolution as the 

 most important break in the animal series, and one which that 

 doctrine could not bridge over. Since then, as Professor Huxley 

 has clearly shown, this gap has been virtually filled by the dis- 

 covery of bird-like reptiles and reptilian birds. Compsognathus 

 and Archseopteryx of the Old World, and Ichthyornis and 

 Hesperornis of the New, are the stepping-stones by which the 



