DINOSA URS. 
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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 of 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 Archaeopteryx of the Old World, and Ichthyornis and 
Hesperornis of the New, are the stepping-stones by which the 
