GENERAL CHARACTERISTICS. 
13 
being formed of a double series of horny lobes in the basal half of the tail, beyond 
which it is single. The head terminates in a flattened snout of variable length, 
and is attached to the body by a short, although muscular neck; while the bulky 
body is much depressed. The toes are more or less webbed. Externally, the back, 
tail, and under-parts of these animals are protected by an armour of quadrangular 
horny shields of varying size, which are arranged in regular longitudinal and 
transverse rows, and are in contact with one another by their edges. In the 
region of the back, and sometimes also on the under surface of the body, these 
horny shields are underlain by a corresponding series of pitted bony plates. In 
the region of the neck, among existing members of the order, these bony plates 
are often irregular in form, and vary in number, but on the back they are always 
quadrangular and broader than long, with a well-marked longitudinal ridge down 
the middle. Such plates form a considerable number of longitudinal rows; each 
plate articulating by its edges with those on either side, while those of each 
transverse row overlap those immediately behind them. When a bony shield is 
developed on the under surface of the body, the number of longitudinal rows of 
plates in existing forms is always more than eight; the transverse rows of plates 
overlapping and each plate being composed of two distinct pieces united together 
by suture. The limbs are provided with five toes in front and four behind; the 
three innermost digits in each foot being furnished with claws. In all crocodiles, 
whether living or extinct, the conical teeth, which may be of very large size, are 
confined to the margins of the jaws, where they are implanted in distinct sockets ; 
while those in use are continually being replaced by fresh ones growing from 
beneath. These animals are further characterised by their nostrils opening at the 
extremity of the snout—which may be either short or long—and by their ears being 
covered with movable lids. 
Such are some of the leading external features of these reptiles, and although 
they would suffice to distinguish them from the living members of the order, 
they are insufficient to determine their true affinities. Laying stress upon the 
above-mentioned characters of their teeth, the naturalist is accordingly compelled 
to resort to the skeleton and soft internal parts for more distinctive characters. 
In the skull all crocodiles are characterised by the quadrate-bone (of which the 
position is indicated in the figure on p. 2) being firmly united with the adjoining 
bones; while a further distinctive feature is to be found in the presence of two 
bony bars on the sides of 
the skull behind the socket 
for the eye, the uppermost 
of these arches being shown 
immediately below the 
letter T in the accompany¬ 
ing figure, while the lower 
and more slender one forms 
the backward continuation of the inferior margin of the eye-socket. The more 
anterior ribs (which, as in other Keptiles, are present in the neck as well as in the 
chest) generally articulate with the backbone by means of two distinct heads; 
and, while collar-bones are wanting, there is a breast-bone and likewise an inter- 
SIDE VIEW OF SKULL OF EXTINCT CROCODILE ( PelagOSaUTUS ). 
0, socket for the eye ; T, temporal pit or fossa. 
