382 
DR. MANTELL ON THE PELOROSAURUS. 
large block of sandstone, and I succeeded, after much labour, in clearing them from 
the stone with their processes nearly entire; in the progress of my task a chevron 
bone of the crocodilian type, 10 inches long (Plate XXII. fig. 8), was laid bare and 
extricated. 
When these splendid fossils were first discovered, I referred them to the Iguanodon ; 
subsequently they were named by Professor Owen Cetiosaurus brevis * ; and lastly. 
Dr. Melville and myself, in my Memoir on the Iguanodon-i-, suggested the necessity 
of adopting a different specific appellation, and proposed that of “ Conyheari we 
were unwilling to remove them from the genus Cetiosaurus, till corroborative evidence 
was obtained to justify the change. 
The description of these vertebrae in detail will be found in the British Association 
Reports for 1841 (p. 97 )? and by Dr. Melville in the Philosophical Transactions, 1849 
(p. 296 ) ; but without figures no adequate idea can be given of the originals:}:. I have 
therefore annexed delineations on a reduced scale, \ linear, Plate XXII., and two 
views of the largest vertebra fths the natural size, Plate XXIV. and XXV. I have 
been induced to add the two last drawings in order that the subject may be fully 
comprehended. 
These vertebrae are distinguished by the subquadrangular form of the articulating 
facets of the centrum or body, and the relative shortness of the antero-posterior dia- 
meter (Plate XXII. fig. 7)- The largest is 71 inches in the transverse, and 6f inches 
in the vertical diameter of the anterior face, and but 6 inches in the posterior: the 
length or antero-posterior dimension is but 3^ inches. The height to the top of the 
spinous process is 13 inches. The diameter of the neural canal, for the spinal marrow, 
is 2 inches. The other three bones are somewhat smaller ; the most distal being only 
6 inches transversely. 
These vertebrae are slightly concave in front, and almost flat behind ; the upper 
part of the anterior face being the deepest, as shown in Plate XXII. fig. 5®. The sides 
of the body are concave, both lengthwise and vertically, with a transverse median 
convexity, as seen in Plate XXII. fig. 5“. 
The inferior surface of the centrum (Plate XXII. fig. 6) is slightly concave in its an- 
tero-posterior diameter, and divided by a longitudinal sulcus into two ridges, whose 
terminations obscurely indicate the position of the hsemapophysial articulations. It 
is noticeable, that in vertebrae of such magnitude, well-defined articulating spaces for 
the chevron bone are not present. 
The neural arch presents the most peculiar characters; it is large, and anchylosed 
to the anterior half of the upper surface of the centrum ; the posterior part of which 
is left free, as shown in fig. 5® and 7, Plate XXII. The anterior oblique processes 
* These vertebrae and the chevron bone, are placed in the same case as the bones of the Iguanodon, in the 
Gallery of Organic Remains of the British Museum. 
t Philosophical Transactions, 1849, p. 297. 
X Sir J. G. Daltell very properly remarks, that “ delineation should be the inseparable accompaniment of 
description in natural history.” 
