6 
REPTILES. 
sion of the jaws into horn-clad beaks. Certain representatives of the extinct 
flying dragons were likewise devoid of teeth; and as in these forms the horn- 
covered jaws were long and narrow, the resemblance to the beak of a bird becomes 
most marked. 
It has already been stated that the vertebrae of Reptiles never articulate by 
means of those saddle-shaped surfaces so characteristic of Birds. They present, 
however, great diversity of structure in this respect. In some cases, for instance, 
as in the fish-lizards, the bodies or central portions of the vertebrae are very short 
from front to back, and have concave surfaces 
both in front and behind for mutual articula¬ 
tion. In marked contrast to this type is the 
LEFT-SIDE VIEW OF A NECK VERTEBRA 
OF A DINOSAUR. 
SIDE AND FRONT VIEWS OF THE BODY OF A VERTEBRA 
OF A FISH-LIZARD. 
b, anterior ball.—After Marsli. 
a, b, attachment of ribs. 
neck vertebra of a Dinosaur, where the anterior end of the body of each vertebra 
forms a convex knob (6), received into a cup at the posterior end of the vertebra 
in advance. 1 In other instances, as in the existing crocodiles and lizards, an 
arrangement pre¬ 
cisely the reverse 
of the last is pre¬ 
sent ; that is to 
say, the ball is at 
the hinder end, and 
the cup at the front 
of the body of the 
vertebra. In a 
few lizards and in 
all snakes the ver¬ 
tebrae are further 
complicated by the 
development of 
additional articular facets, taking the form of wedge-like projections from one 
vertebra, which are received into cavern-like excavations in the adjacent one. 
FRONT AND BACK VIEWS OF A VERTEBRA OF A SNAKE. 
zi indicates the additional articular process, which is received into the cavity zi 1 . 
i It should be mentioned that in this figure only the portion of which b is the extremity corresponds with the 
whole of the specimen represented in the other figure on the same line. 
