ICHTHYOSAURUS. 
179 
each other. It is quite certain, therefore, that 
such large and bulky creatures as the Ich- 
thyosauri, having their vertebraj constructed 
after the manner of fishes, had they been 
furnished with legs instead of paddles, could 
uot have moved on land without injury to 
their backs.* 
mbs. 
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 
cana which exists in no other animals; the annular part (PI. 
12, D a. and E a.) being neither consolidated with the body of 
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 socketjoint, 
art ” ® Conybeare adds, that this mode of 
t iculation co-operates with the cup-shaped form of the interver- 
^ rai joints, m giving flexibility to the vertebral column, ana 
dated'*^^ vibratory motions; for, had these parts been consoli- 
lock 1 quadrupeds, their articulating processes must have 
^ whole column together, so as to render such a motion 
vi impossible ; but by means of this joint every part 
^6 s to that motion. The tubercle by which the transverse 
pop lysis of the head of the rib articulates with the vertebra, is 
