ICHTHYOSAURUS. 179 
each other. It is quite certain, therefore, that 
such large and bulky creatures as the Ich- 
thyosauri, having their vertebrae constructed 
after the manner of fishes, had they been 
furnished with legs instead of paddles, could 
not have moved on land without injury to their 
backs.* 
The ribs were slender, and most of them 
bifurcated at the top : they were also conti- 
nuous along the whole vertebral column, from 
the head to the pelvis, (see Plates 7, 8, 9) ; 
and in this respect agree with the structure of 
modern Lizards. A considerable number of 
them were united in front across the chest : 
their mode of articulation may be seen in PI. 14. 
* Sir E. Home has further remarked a peculiarity of the spinal 
canal, which exists in no other animals; the annular part (PI. 
12, D a. and E a.) being neither consolidated with the body of 
the vertebra, as in quadrupeds; nor connected by a suture, as in 
Crocodiles ; but remaining always distinct, and articulating by a 
peculiar joint, resembling a compressed oval ball and socket joint, 
(D g. and E g.). And Mr. Conybeare adds, that this mode of 
articulation co-operates with the cup- shaped form of the interver- 
tebral joints, in giving flexibility to the vertebral column, and 
assisting its vibratory motions ; for, had these parts been conso- 
lidated, as in quadrupeds, their articulating processes must have 
locked the whole column together, so as to render such a motion 
of its parts impossible ; but by means of this joint every part 
yields to that motion. The tubercle by which the transverse 
apophysis of the head of the rib articulates with the vertebra, is 
seen at d. 
