16 FOSSIL REPTILIA OF THE 



I have not met with this character in the corresponding vertebrae of other Saurians. 

 In the vertical direction the sides of the centrum in the posterior caudals converge at 

 almost a right angle to the inferior groove. The greater breadth of the centrum, in 

 proportion to its height, may still be discerned in the terminal caudal vertebrae (fig. 6): 

 thus in the centrum 2 inches 2 lines long, the breadth was 1 inch 10 lines, and the 

 height only 1 inch 3 lines. Here the bases of the short, but fore-and-aft extended, 

 haemapophyses appear to be confluent, as in fig. 7 ; but their peculiar shape would 

 serve to distinguish them from a haemal arch of an Iguanodon. 



Bones of the Extremities. — Scapular arch. 



The scapula of the Hylaeosaurus (T. IV, 51) is longer and narrower than in the 

 Monitors and Iguanas, adhering in this respect to the Crocodilian type, but most 

 resembling in the shape of its blade or body, that of the genus Scincus. It differs, 

 however, from the scapulae of all known reptiles, and indicates an approach to the 

 Mammalian type, by the production of a strong obtuse acromial ridge, separated by a 

 deep and wide groove from the humeral and coracoid articular surfaces. The blade 

 of the scapula is long, flattened, slightly convex on the inner and proportionally 

 concave on the outer surface: the anterior margin is convex, the posterior one 

 concave ; the upper extremity or base truncate, slightly convex, with the posterior 

 angle a little produced, the anterior angle rounded off. On the outer side of the 

 scapula two broad convex ridges descend and converge to form the beginning of a thick 

 and strong spine, at fourteen inches distance from the base ; this then expands into the 

 thick acromial ridge, which extends transversely, and is continued forwards as a long 

 subprismatic process from the anterior angle of the head of the scapula. This process, 

 the homologue of which exists in the scapula of the Iguanodon, and more developed 

 in that of the Megalosaurus, is broken off in the present specimen about four inches 

 from the neck of the scapula, with which it forms a right angle. The acromion is 

 perforated at the base of its anterior prolongation by a foramen analogous to the 

 supraspinal one in the scapula of the Edentate Mammalia. Besides the scapulas 

 preserved in the connected part of the skeleton, there is, in the Mantellian Museum, a 

 nearly entire and detached scapula of larger size, discovered, in connection with many 

 other bones of the skeleton, in a layer of blue clay near Bolney, in Sussex, and indi- 

 cating the connected part of the skeleton first discovered in 1832 to have belonged to 

 an immature individual. The dimensions of this scapula are as follows : 



