OB&AKIZATION O? THE OENITHOSAURIA. 97 



resemblances to certain groups of reptiles, especially in the form of 

 the intervertebral articulation ; but this structure is coupled with 

 so many other characters (especially in tbe neck and sacrum) which 

 are not found in reptiles, that, unless the predominant resemblances 

 of the rest of the skeleton prove to be with the Eeptilia, it would 

 be philosophical to infer that other groups of animals besides 

 reptiles possess procoelous vertebrae. We have already seen that 

 opisthocoelian vertebrae occur in every division of the vertebrata ; 

 and this fact, when considered in connexion with the variations of 

 intervertebral cliaracters in different vertebrate classes, would 

 appear to render the procoelous articulation less important than 

 it has been supposed to be by morphological anatomists. 



The pectoral and sternal bones are about as markedly avian as is 

 the skull. The sternum appears to differ from that of most birds in 

 being as broad as long, while it is probably relatively muclj shorter, 

 Tliekeelis only well developed at the proximal end as in the Grannet 5 

 and the semicircular posterior border to the bone, observable in 

 some Grerman specimens of Ornithosaurs, is a character not seen in 

 birds. Von Meyer reports, in some specimens oi Bhamphorhynchus, 

 that the lateral portions of the sternum to which the sternal ribs 

 are attached are distinct ossifications, as they are in at least some 

 young birds, such as the chicken. The sternal ribs which articulate 

 with the sternum are ossified, as is the case with birds ; and there 

 is a resemblance to birds in that only a few join the sternum. 

 But there is a striking difference from birds in that, behind the 

 sternum, V-shaped abdominal ribs are freely developed, as in 

 Hatteria &c,, and these structures do not occur in birds. I have 

 moreover never seen in an Ornithosaur any trace of the epipleural 

 element characteristic oiHatteria, of Crocodiles, andof Chelonians, 

 and so often seen in the ribs of birds ; so that, if developed, it 

 must have been cartilaginous. 



The right angle at which the coracoid meets the scapula is cha^ 

 racteristic of carinate birds. The coracoid much resembles the 

 bone in birds, yet has distinctive differences. The bird-like fea- 

 tures are the elongated form, rounded inner side, and compressed 

 outer margin of the bone ; the distal articulation with the sternum 

 is concave from within outward, and convex from before backward, 

 as in birds ; and the proximal articulation with the scapula simi- 

 larly looks backward. But there is a difference, in Cretaceous 

 species, from the coracoid of a bird in that the bone is not pro- 

 longed proximally beyond the articulation for the humerus. 



