554 BRITISH FOSSIL REPTILES. 



entire, 3 inches 3 lines. At the opposite or hinder end the breadth was less, and the 

 height ajjparently greater, whence it may be inferred that this vertebra was near to the 

 hinder end of the sacrum. 



The right half of the anterior, flat, smooth but irregularly indented, articular surface 

 of the centrum is nearly entire. Extending, as far as the origin of the pre-parapophysis, 

 ;;, which is preserved, and wanting only part of its upper surface, the entire transverse 

 extent can be estimated, as above noted. 



The under surface of the centrum (PI. 62, fig. G) is more convex across than in the 

 subject of fig. 1, PI. 61, concomitantly with its greater extent in the present vertebra. 

 The longitudinal contour of the luider surface (PI. 62, fig. 5) is more uniformly concave. 

 The margin of both articular ends is eroded. The aperture of the lateral excavation 

 (ib., fig. 4, c') is 1 inch 5 lines in longitudinal extent; but the cavity is continued 10 

 lines further above the pre-parapophysis (ib.,jy) ; the depth of the excavation at the 

 middle of the vertebra is 1 inch 3 lines. The smooth compact crust of the centrum 

 passes, without fracture, over the free lateral tract (ib., fig. 5, c). The vertically convex 

 border of the floor of the cavity is somewhat thicker than in first-described sacral 

 vertebra, but similarly shows a natural condition and contour. The upper surface of the 

 floor of the cavity shows a fine crack (outside the letter / in fig. 4) as if the inner half of 

 that floor, with the adjoining part of the centrum [p) supporting the base of the neural 

 arch had been slightly depressed. 



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

 outhne in figs. 4 and C. 



The subject of figs. 1, 2, 3, PI. 02, transmitted at the same time with the vertebrae 

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

 vmder surface and of 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 «, fig. 2, in the irregular impressions of 

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

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

 nientously 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. Abo've 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 



