Animal Dentition DDS 
setting go, only with the dentition of dolphins, 
which, as we have already shown, is of a 
degenerate and retrograde type. In conse- 
quence, indeed, of the simple structure and 
general similarity in form of the individual 
teeth, the dentition of existing reptiles forms 
a far less interesting subject of study than 
that of mammals, and it will therefore be = 
treated much more briefly on the present HEHE eh WDhewoNalom Ge Toa, 
occasion. On the other hand, the dentition of many of the numerous extinct groups 
of reptiles displays greater variation, and therefore affords a more suitable subject for 
a popular article. 
The teeth of crocodiles and alligators, in addition to their large size, conical form, 
and implantation in distinct sockets, are characterised by being confined to the margins 
of the jaws, and also by the circumstance that a certain number are much superior 
in size to the rest, these enlarged teeth occupying the highest points of the festoons 
into which the margins of the jaws are thrown. One of these enlarged teeth of the 
lower jaw—the fourth from the front—affords one of the easiest ways of distinguishing 
between crocodiles on the one hand and alligators and their near relatives the caimans 
of South America on the other. In a crocodile (Fig. 3) this large fourth lower tooth 
bites into a notch on the side of the upper jaw, and is thus visible externally when the 
mouth is closed; whereas in an alligator or a caiman the same tooth (Fig. 4) is received 
into a pit in the upper jaw, and is consequently concealed when the mouth is shut. 
Sometimes, indeed, the fourth lower tooth actually pierces the upper jaw of very old 
alligators. A further distinction between the dentition of the two groups is to be 
found in the circumstance that, in crocodiles, the teeth of the two jaws interlock, 
instead of the upper ones biting outside the lower ones; while the number of teeth, 
especially in the lower jaw, is much greater in crocodiles than in alligators and caimans, 
which have invariably only fifteen lower pairs. Of course, I expect to be told that I 
am wrong in this, and that Indian “alligators” do not conform to this definition. 
But then, in the scientific acceptation of the term, there are no alligators in India, the 
reptiles commonly thus miscalled being true crocodiles. As a matter of fact, alligators 
we represented only by one or two species in North America and a third in China, 
while caimans are confined to Central and South America; all the other existing 
members of the group being crocodiles or gharials. 
As the teeth of the majority of lizards are of comparatively small size, they are 
not well adapted for illustration, and my remarks concerning them will consequently 
be brief. The largest of all lizards are the monitors of the Old World and Australia, 
and in these the teeth (Fig. 5) are simple laterally compressed and recurved cones, 
with broad, expanded bases fixed to the sides of the jaws, to which they may become 
welded. They are comparatively few in number, are limited to the margins of the 
jaws, and in their mode of succession much resemble those of crocodiles and alligators. 
Teeth of this type indicate, it need hardly be said, carnivorous 
habits on the part of thei owners. 
From their blunted summits it might seem probable that 
the teeth of the large Australian and Papuan broad-toothed 
skinks of the genus Tiliqua (Fig. 6) were adapted for a vegetable 
diet. This, however, does not appear to be really the case, 
since the smaller lizards of the same group are insectivorous, 
and it is therefore probable that the blunt teeth of the 
Fig. 6. Jaws of Giant Skink. Australasian forms are used for crushing the hard coverings of 
