﻿WEALDEN. 



23 



§ 3. BOTHRIOSPONDYLUS PROM THE WEALDEN. 



A. — Bothriospondylus elongatus, Ow. Plate VII. 



Although my opinion of the nature of this fossil, figured in the Monograph on 

 Wealden Dinosaurs, Palseontograph. Soc. Volume for 1854, Tab. X, as "the tympanic 

 bone of an Iguanodon ?" was subsequently modified, as is well known to those who 

 sympathised with, and assisted by materials in, the progress of my work on * British 

 Fossil Reptiles,' the first published opinion (1870) of the vertebral nature of the fossil, 

 as far as I am aware, was that of H. G. Seeley, Esq., P.G.S., to which I shall presently 

 refer, retaining my conviction of the closer agreement of the vertebra in question with the 

 subjects of Plates III — VI of the present Monograph than with those of any volant 

 animal. 



The species, Bothriospondylus elongatus, is represented by the centrum of a dorso- 

 lumbar or trunk-vertebra, from Tilgate, exceeding in the proportion of length to depth 

 that of Bothriospondylus robustus (PI. VI), in a greater degree than this is exceeded 

 by the corresponding vertebra of Bothriospondylus suffossus (PI. V). The ratio of 

 augmentation of bulk also becomes greater as we pass or ascend from the small Kim- 

 meridgian type to the colossal Wealden form. 



The length of the present fossil centrum is eight inches, and it must have been more 

 when perfect, for both ends, and especially the fore or subconvex one, have undergone 

 fracture and abrasion. The fractures at the end, a, however, bring to light the unusually 

 large cancelli, some of them admitting the end of the thumb ; and this structure, 

 associated with the length and depth of the lateral depression, PI. VII,/, give-the grounds 

 for referring the specimen to the genus, or group, Bothriospondylus. 



The natural surface of the bone is smooth, or finely striate lengthwise, towards the 

 articular ends, as in Bothr. suffossus, PI. V, fig. 1. As in that vertebra, also, the centrum 

 expands to both ends, but less gradually, the contracted micUpart being relatively longer ; 

 its transverse section is less cylindrical, the lower surface being more flattened, less 

 convex transversely, and the breadth of the middle of the centrum, 3 inches 6 lines, being 

 greater in proportion to the height measured from the margin of the lateral depression to 

 the under surface, which is 2 inches 6 lines. 



The part of the centrum above the depression,/, becomes, as in the smaller vertebras, 

 very thin ; and, as with the portion preserved in Bothriospondylus robustus, the plate 

 inclines outward as it ascends, indicative of a neural arch of greater breadth than the 

 centrum below. 



d 



