WEALDEN DINOSAURS. 333 



proportions of those parts which have not before been noticed in any Dinosaurian, or 

 in the dorsal vertebrae of any other reptile, recent or fossil. 



That these vertebrae are from the fore part of the chest is indicated, according to 

 the analogy of the CrocodiUa and of the Iguanodon, by the articular surfaces for both 

 the head and tubercle of the rib, and by the progressive ascent of the surface, p, 

 for the head of the rib, as the vertebrae recede in position. By reference to the 

 PL 24, it will be seen that this surface slightly projects, and is situated upon the 

 neurapophysial suture in the first, p, «*. but above that suture, supported wholly by 

 the neurapophysis, in the third of those vertebrae, p, ns". The megalosaurian 

 character of all of the vertebrae is shown by the great, though regular and gradual 

 constriction of the centrum between its articular ends, by the corresponding depth of 

 the concave contour lengthwise, and by the almost circular form of the transverse 

 section of the lower two thirds of the centrum. The non-articular surface of the 

 centrum is smooth and polished, with some longitudinal grooves and ridges near the 

 expanded ends, the bodies of which are thick and rounded. The side of the centrum 

 is moderately hollowed below the neural suture, and swells out, becoming convex 

 vertically, before bending round to the under surface. There is a rough tuberosity^ 

 t, at the upper and back part of the centrum, which may be contributed by the 

 base of the neurapophysis. 



The neural arch offers the same complex structure as in other Dinosauria ■■ a com- 

 pressed plate, b, extends obliquely backward from the parapophysis, p, to the diapo- 

 physis, cl; the latter being supported by a stronger buttress extending outward from 

 near the back part of the base of the neurapophysis, and being slightly inclined for- 

 ward. Three deep depressions, probably receiving parts of the lungs in the living 

 animal, divide these lamelliforra buttresses from each other, and from the bases of the 

 anterior, :, and posterior, z, zygapophyses. The articular surface of the anterior one 

 looks upward and slightly inward, that of the other, •, downward and slightly 

 outward, both being nearly horizontal. The neural platform extends from the outer 

 margin of the prezygapophyses, z, to the fore part of the postzygapophyses, z' . The 

 back part of the base of the neural spine is formed by two strong ridges, continued 

 each from the whole upper part of the postzygapophysis, leaving an intermediate fossa 

 for the implantation of a ligament : the base extends forward to the interspace between 

 the prezygapophyses, being coextensive lengthwise with the vertebral centrum. 



In the anterior of the three vertebrae the spine, ns, as it rises, slightly decreases in 

 fore-and-aft extent, and then as gradually regains its dimension in that direction : after 

 contracting transversely to a thickness of eight lines, when two inches above its 

 base, it gradually expands to a thickness of one inch and a half at its summit, which 

 forms a rough tuberosity, bevelled off obliquely from before upward and backward 

 to within a third of its hinder border, which is flat : the whole height of this spine is 

 nine inches, the vertical extent of the entire vertebra being thirteen inches six lines. 



