460 
of the inferior surface being less; and from the posterior caudal 
vertebree of the Iguanodon, which slightly increases in length, in 
being less compressed and the centrum not having a triangular form ; 
the slender terminal caudal vertebre of the Iguanodon are also hex- 
agonal, and not cylindrical as in the Cetiosaurus. 
As there is no known extinct saurian which can so nearly com- 
pete in size with the Cetiosaurus as the Iguanodon, it is fortunate, 
Prof. Owen observes, that the distinguishing characters are so well 
marked and easily recognizable. 
Dorsal vertebra.—The only portion of a dorsal vertebra described 
in the memoir is the extremity of a spinous process, the posterior 
surface of which is rough and flattened, 4 inches across, at about 
the same distance below the end of the spine; the sides are traversed 
to a certain extent by a longitudinal ridge, anterior to which they 
are concave and smooth, but their anterior margin is again flattened 
and rough, though it is not so broad as the posterior. 
In referring all the vertebre described in this paper to the same 
species of saurian, Prof. Owen admits that they present a somewhat 
greater variety of form and proportion in different regions of the 
tail than is observable in that part of the vertebral column im the 
smaller and recent species of Crocodile or Lizard; not only beco- 
ming larger in proportion to their thickness, but increasing slightly in 
length for a short distance as they recede from the sacrum. They 
appear likewise to exchange from a cylindrical to a subtriedral 
form of the body, but to resume the cylindrical shape in the termi- 
nal half of the tail. ‘These modifications, he says, are possible, as 
in the Plesiosaurus brachydeirus ‘still greater discrepancies in the 
proportions of the vertebre prevail ; and they are infericr in degree 
to any of the modifications which distinguish the vertebrze of known 
genera of saurians from those under consideration, in pointing at 
their distinguishing features from the hitherto known sauria; and 
in thus treating ef them collectively, the inference that they belong 
to the same gigantic species is, the author observes, almost irresist- 
ible, that they belong to a new and distinct genus, which, on ac- 
count of the vertebre approximating im size and structure to the 
vertebrz of the whale, he has termed Cetiosaurus. 
In the cuttings for the London and Birmingham Railway near 
Blisworth, there were found, scattered over an area of 12 feet by 8 
feet, the following remains :—1. A bone resembling the episternal 
- of an Ichthyosaurus, the length or antero-posterior extent of the 
preserved portion of the median plate being 14 foot, and the breadth 
of the posterior fractured ‘end 5 inches, from which it gradually ex- 
pands to the root of the side branches, where its breadth is 1 foot. 
From its obtuse termination _to the end of the longest branch is 24 
feet, and from this end to that of the opposite branch 41 feet. 
2. The remains of a coracoid and scapula apparatus of equally gi- 
gantic proportions. 3. A fragment, considered to be the shaft of 
a humerus, 1 foot 9 inches in length, 6 inches in diameter across the 
middle and 8 inches across the widest end. 4. A portion of the oppo- 
site humerus. 5. Another fragment, believed to be part of a radius 
.or ulna, about a yard in length, 6 inches across the proximal end, 
