KIMMERIDGIAN DINOSAURS. 559 



This character is strongly marked in dorsal vertebrae of the present genus, and with 

 modifications wliich could hardly have been illustrated or made clear without the 

 above-cited figures of the vertebrae of previously defined Diiiosaurian genera. In 

 these, however, the degree of complexity of the neural platform varies ; it is least 

 marked in the smaller and more crocodilioid genus Scelidosauriis {Dinosauria, Plates 

 51 and 52). 



The vertebra of Omosaurus — the subject oi' Dinosauria,' Plates 65, fig. 1, and 06 — has 

 come from the middle of the trunk. This is inferred from the position of the surface, ;j, 

 for the head of the rib, which has risen from the centrum, or base of the neural arch, to near 

 itssunnnit, where, with its diapophysial productions, ,/, ,/, the arch expands to a breadth of 

 14 inches 6 lines ; the breadth (in the same direction, transversely) of the centrum being 

 5 inches 3 lines. The vertical diameter of the middle of the articular surface of the 

 centrum is 4 inches 9 lines ; the height of the vertebra to the base of the neural spine is 

 II inches. This spine has been worked out entire only in the above-described cervical 

 and caudal vertebrae ; but there are indications justifying an estimate of its length in 

 the dorsal series, at from 6 to 8 inches. 



Thus, the dorsal vertebra, affording material for the present description, which 

 has a breadth, as above shown, of one foot two and a half inches, had a height of at 

 least one foot and a half. 



The fore-and-aft dimension of the centrum (PI. 66, fig. 3) is 4 inches. The anterior 

 surface (ib., «), where it varies from flatness, is toward convexity, but in the feeblest 

 degree ; the posterior surface (ib., j) is very slightly, but more equably, concave. The 

 free surface of the centrum is moderately concave longitudinally ; slightly depressed 

 at /, beneath the base of the neural arch. The tissue throughout the vertebra is more 

 compact than in Cetiosaurus {' I)inosauria' PI. 70). 



The neurapophyses (PL 05, fig. 1, n p) have coalesced with the centrum ; they quickly 

 narrow transversely, above their base, to a thickness of half an inch, more gradually 

 contract in fore-and-aft dimension (PI. 06, fig. '2,np) to two inches and a half Over- 

 arching the neural canal (PI. 05, fig. I, «)>they meet and coalesce about one inch and nine 

 lines above the centrum, whence their compact coalesced mass rises above the crown of 

 the arch, expanding to a height of five inches (posteriorly, PI. 66, fig. I) before giving 

 off the neural spine (ib., 71 s)- 



At three inches above the base the outer surface of the neurapophysis is excavated by 

 a smooth oval cavity (ib., fig. 2, p), 1 inch 9 lines in vertical, 1 inch lines in 

 transverse, diameter, and about y lines in depth. To this cavity was adapted the ' head 

 of the rib :' for this part there is no parapophysis, or outstanding process. Below the 

 capitular cavity the outer surface of the neurapophysis is divided from the hinder surface 

 by a low obtuse ridge or angle (ib., ib., e) ; a broader ridge (ib., ib., a), also low 

 and obtuse, rises along the middle of the outer surface of the neurapophysis, and 

 expands to form the lower margin of the costal pit. In advance of this jut the 



8d 



