622 BRITISH FOSSIL REPTILES. 



Order. DINOSAURIA. 

 Genus — Chondrosteosaurus. 



Species — Chondrosteosaurus (jigas, Owen. (' Dinosauria,' Plates 79 — 82.) 



The flatness of the under surface of the vertebra figured in Plates 79 — 82 recalled the 

 character of that of Boihriospondylus snffossus (p. 551, Plate 61), and, with the pre- 

 dominance of the transverse over the vertical diameter, suggested that it also might have 

 come from the sacral series. 



The hemispheroid convexity, however, of the anterior end, notwithstanding abrasion of 

 the articular surface itself, and the proof of its truly indicating such form given by the 

 more perfect preservation of that surface in the opposite concave articular end (Plate 80), 

 too plainly pointed to a much more forward position of this remarkable vertebra in the 

 backbone series of the huge Reptile which it represents. 



That the vertebra is from the fore part of the trunk may be inferred from the 

 presence, on each side, of both a parapophysis (PL 79, ;j) and a diapophysis (ib., d), 

 indicative of the bifurcation of the proximal end of the rib into a capitular and a 

 tubercular articulating process. 



The portion of neural canal preserved (Plates 80 and 81, «) gives the vertical 

 diameter of the centrum. There is no indication in the concave articular surface of that 

 diameter having been diminished by posthumous pressure. The gentle transverse con- 

 cavity of so much of the broad under surface as is preserved (Plate 79) is evidently natural. 

 The deep depression (Plate 82, fig. 1,/) on each side of the centrum betvpeen the par- 

 and di-apophyses recalls a vertebral character of the genus Bothriospondylus. 



The parapophysis (Plate 79, fig. 1, p) projects from the level of the under surface: 

 it commences behind, four inches from that end of the vertebra, as an extension of the 

 lower border of the centrum, curving outward and gaining vertical thickness as the 

 process advances (Plate 82, fig. 1, p), the fore part of the base of the process occupying 

 the lower vertical half of the centrum, and terminating very near to the beginning of the 

 anterior articular ball. 



The neurapophysis (Plates 80, 81, 82, w«), which has coalesced with the centrum, 

 begins to rise about two inches in advance of the hinder cup. The part of the broken 

 base there preserved yields a transverse thickness of 3^ inches. Anterior to this the 

 upper surface of the centrum has been abraded to the level of the neural canal, but 

 sufficient is preserved to show that the neurapophysis loses thickness at the middle of the 

 vertebra, and appears to regain it as it approaches the anterior ball (Plate 81, fig. 1). 



The base of the diapophysis (Plate 81, fig. 1, rf), at the part of the neurapophysis pre- 



