•30 THE ANATOMY OF VERTEBRATED ANIMALS. 



ossified sternal ribs, and splint-like abdominal ribs. Tlie 

 sternum is broad, and, unlike that of other Ite})tilia, is very 

 completely ossified, and bears a strong median ciest on the 

 anterior part of its ventral surface. No median posterior pro- 

 longation has been observed in connection with it. 



The brain-case is more rounded and bird-like than in the 

 other Reptilia, and, in many other respects, the skull ap- 

 proaches that of birds. Thus, the occipital condyle is on the 

 base of the skull, not on its posterior face ; the cranial bones 

 anchylosed very early ; the orbits are very large, and the ex- 

 ternal nares are situated close to them. The premaxilte are 

 very large, the maxillae slender, and the dentary pieces of the 

 mandible are fused together into one bony mass, without any 

 trace of a symphysial suture. 



The resemblance to birds is still further increased, in some 

 species, by the presence of wide lachrymo-nasal fossae between 

 the orbits and the nasal cavities, and by the prolongation of 

 the extremities of the premaxillse and of the symphysial part 

 of the mandible into sharp, beak-like processes, which appear 

 to have been covered with homy sheaths. But the reptilian 

 type is kept up by the presence of a distinct post-frontal, which 

 unites with the squamosal and thus gives rise to a supra- 

 temporal fossa. The post-frontal and the jugal unite behind 

 the orbit, in LacertUian fashion ; and both the upper and the 

 lower jaws contain teeth. The sclerotic is supported by a ring 

 of bones, as in many other Sauropsida. 



The scapula and the coracoid are wholly unlike these 

 structures in any other 8auropsida^ but are extremely similar 

 to the same parts in birds, and indeed to the shoulder-girdle 

 of the less reptilian Carinatm. The scapula is slender and 

 blade-like, and its long axis is inclined, at less than a right 

 angle, to that of the coracoid. The glenoidal surface is cylin- 

 droidal, concave from above downward, convex from side to 

 side. The coracoid, elongated and comparatively narrow, is 

 devoid of fontanelle, epicoracoid, or procoracoid. 



No trace of any clavicle has been discovered. 



The humerus has a great deltoid ridge or process. Tlie 

 radius and ulna are equal in size and separate. There are 

 four distinct metacarpal bones, that on the ulnar side being 

 very much stronger, though not longer, than the others. An- 

 other styliform bone attached to the carpus does not appear 

 to have belonged to the metacarpal series. The radial meta- 

 carpal bears two phalanges ; the second, three ; the third, four, 

 BO that these represent the poUex and the succeeding digits 



