﻿KIMMERIDGE CLAY. 



19 



The proportion broken away from the left side of the present vertebra is indicated in 

 outline in figs. 4 and 6. 



The subject of figs. 1, 2, 3. PI. IV, transmitted at the same time with the vertebras 

 above described, and from the same locality, I refer, from the superficial characters of the 

 under and one of the terminal surfaces of the centrum, to the same genus and species of 

 Dinosaur, and it probably formed part of the same individual. 



The flattened surface of the centrum, at a, fig. 2, in the irregular impressions of 

 its otherwise smooth surface closely accords with the one, b, of the subject of fig. 5, 

 to which it adapts itself sufficiently closely to suggest that it may have been liga- 

 mentously articulated thereto. The opposite surface (ib., fig. 1 and fig. 2, 6) is not so 

 impressed, is slightly convex and smoother, and indicates a joint with the succeeding 

 vertebra admitting of more movement. I infer, therefore, that the present specimen is the 

 centrum of the last sacral vertebra, and that the end articulating with the first caudal 

 vertebra had resumed more of the usual vertical proportions of the centrum. The para- 

 pophysis (p), with the irregular syndesmosal surface, has a greater extent, both vertically 

 and lengthwise. Above it extends the narrow fractured surface of the broken off base of 

 the neurapophysis. The floor of the neural canal (fig. 1, n ) is preserved, which is 

 concave lengthwise as well as across, sinking somewhat into the substance of the centrum. 

 Its diameter midway between the two ends is 7 lines. 



The lateral excavations of the centrum appear to have ceased at this vertebra, and 

 probably were not resumed in the caudal series. It has been fractured and somewhat 

 distorted by posthumous violence : but this has not affected the contour of the under 

 surface of the centrum (ib., fig. 3), or the vertical proportions of this element, any more 

 than in the case of the two previously described sacrals. 



In four centrums of dorsal or dorso-lumbar vertebras of Botliriospondylus suffossus, 

 forming part of the same series transmitted from the Kimmeridge Clay of Swindon, the 

 characteristic excavations are conspicuous and with longer apertures than in the sacral 

 vertebrae, where these are interrupted by the broad articular parapophyses. No trace of 

 the latter processes are present in the trunk vertebras of which the type is selected for the 

 subjects of Plate V. 



The centrum is subcompressed (fig. 2) ; its sides moderately concave lengthwise 

 (fig. 1), with one end feebly convex, a, the opposite end rather more concave, b. I regard 

 the latter as the hinder one, and the trunk-vertebras to be, as in Streptospoiidglus, of 

 the opisthoccelian type. The free surface of the centrum is smooth, save near the 

 articular ends, where there are low longitudinal risings and shallow channels, as 

 shown in fig. 1, PI. VI. The under surface (ib., fig. 4) is perforated by two or more 

 small vascular (venous) canals near the articular ends. 



The fore end (ib., fig. 2) has a somewhat irregular surface. The hind one, which has 

 suffered less from compression (ib., fig. 3), shows a similar coarse pitting and rising at the 



