DR. MANTELL ON THE PELOROSAURUS. 
383 
(Plate XXII. fig. 5®, g, g) project directly forwards, and advance over the exposed 
part of the body of the contiguous vertebra (Plate XXII.* fig. 7); as there are no 
posterior oblique processes, the anterior are received in depressions on each side the 
spinous process (see Plate XXII. fig. 5 and 7 h, h). The transverse processes (f,f) 
are very strong and short, and project at nearly right angles from the body ; the 
spinous process (e) is short and thick. 
In Plate XXII. fig. 7, the four vertebrae are represented in a consecutive line, for the 
purpose of explaining the mode of articulation above described, but it is doubtful 
whether the two posterior bones are in their natural position ; it seems probable that 
there was an intermediate vertebra between the second and third, and between the 
third and fourth, so that two more would be required to complete the series. The 
haemapophysis or chevron bone, Plate XXII. fig. 8, is obviously too small for articula- 
tion with either of the above vertebrae ; it is however important, as showing the 
crocodilian modification of this caudal element of the gigantic original. 
Median caudal vertehrce, Plate XXIII. fig. 1 and 3 , and Plate XXVI. — From the same 
quarry I obtained two vertebrae belonging in all probability to the middle part of the 
tail; and which, though scarcely large enough to appertain to the same individual as 
the above anterior caudal, present such characters as might be expected in the more 
distal part of the same region. The centrum of the largest specimen (Plate XXIII. 
fig. 10 and Plate XXVI.) is 7\ inches long ; the transverse diameter of the anterior face 
is 5 inches, the vertical inches ; height to the top of the spine 5 ^ inches. Both the 
facets of the centrum are slightly concave, and are most deeply excavated in the 
upper part, as in the large anterior caudals. The neural arch is anchylosed to the 
anterior half of the body, the posterior part being uncovered. The inferior surface 
(Plate XXIII. fig. 10® c) is concave antero-posteriorly, and two slightly elevated ridges 
terminate behind in distinct hsemapophysial surfaces {k, h), which are if inch apart, 
and are evidently fitted for articulation with a chevron bone of the type already 
described (Plate XXII. fig. 8). 
Distal caudal vertebra, Plate XXIII. fig. 11. — In referring the unique caudal here 
figured to the same category as the preceding, I olfer the suggestion as only probable. 
The centrum is of a subcylindrical form, 4^ inches long, and slightly concave on both 
facets. The most remarkable feature in this bone is the anchylosis or rather con- 
fluence of the heads of the chevron bone with the body (Plate XXIII. fig. 1 1 j,j), a cha- 
racter common in fishes, but which, I believe, is unknown in reptiles, save in one 
genus, the fossil animal of Msestricht, the Mosasaurus, whose occurrence in the En- 
glish chalk was first ascertained in 1820 , by my discovery of two concavo-convex 
caudals with confluent chevron bones*. The remarks of the illustrious Cuvier on 
the caudal vertebrae of the Mosasaurus, are in every respect applicable to the speci- 
men under consideration. After mentioning the median caudals as having “a leur 
face inferieure deux petites facettes pour porter Vos en chevron," he describes the more 
* Geology of the South Downs, Plates XXXIII. and XLI. 
