ANIMAL DENTITION.* 
By R. LypEKxrmr. 
Il, REPTILES. 
IRDS, as we know them at the present day, are totally devoid of teeth, and do 
not therefore come within the purview of the present series of articles. Never- 
theless, during periods relatively remote im the earth’s history, when the Chalk of the 
Chiltern Hills and the still earlier Oolites of the Cotswolds were being deposited as 
mud or slime on the ocean bed, there flourished birds with a full armature of sharp and 
conical teeth in their beak-like jaws. These toothed birds of the Chalk period were in 
other respects similar in general structure to their modern representatives, but some 
at least of the Oolitic species retained the long lizard-like tails, carrying a pair of 
feathers at eacli joit, of their presumably reptilian ancestors. So far as can be 
determined, the teeth of these early birds were very similar to those of certain extinct 
reptiles, such as the flyimg pterodactyles, being implanted in distinct’ sockets, and 
probably replaced irregularly, after the manner of those of modern crocodiles. 
Certain reptiles, such as the modern turtles and tortoises, together with some of the 
pterodactyles and a few other types long since extinct, have followed the same fashion 
as birds im discarding teeth in favour of horn-clad beaks. If, moreover, according to 
popular usage, frogs, toads, salamanders, newts, and the lke (which, on account of their 
fish-like structure in the earlier stages of their existence, are classed by naturalists as 
a group apart) are regarded as reptiles, there will be certain kinds, such as most 
toads and some tree-frogs, that have neither teeth nor horny beaks. One true reptile 
comes indeed yery near to this condition, so far at least as its mouth is concerned, 
in which there are only a very few almost, if not entirely, functionless teeth of small 
size. This is the curious ege-eating snake (Dasypeltis scaber) of South Africa, which, 
as its name implies, lives by swallowing the eggs of birds, when these are obtainable. 
For a small-mouthed animal to crush a large egg in its mouth would result in the 
loss of much of the succulent contents, of the former. Accordingly, the snake is 
furnished with a crushing-apparatus in its throat. This apparatus is formed by bony 
spines from the underside 
of the neck-vertebre pro- 
jecting into the throat, where 
they are capped with enamel, 
and thus resemble teeth in 
appearance, as they do in 
function. If, however, we 
regard teeth as structures 
originally independent of the 
skeleton, it is evident that 
the so-called teeth of this 
remarkable snake do not 
properly come under that 
category. — 
Apart from the above- 
5 p A Wig. 1. The Open Jaws of a Crocodile, showing the 
mentioned exceptions, all Enlarged Fourth Lower Tooth (A) 
* The first of these articles appeared on page 109 of this Volume. 
221 
