GENERAL CHARACTERISTICS. 
5 
jaws by two or more roots; while in no cases are their crowns complicated by the 
presence of infoldings of enamel. The simplest type of reptilian tooth is in the 
form of a cone; such conical teeth being confined to the margins of the jaws, 
where, as among crocodiles, they may be implanted in distinct sockets, or, as in 
the extinct fish-lizards, 
in an open groove. In 
other cases, as among 
lizards, teeth of the same 
general type may be 
united by a bony deposit 
either to the summit or 
to one side of the margin 
of the jaw. In place 
of the one regular re¬ 
placement, characteris¬ 
ing the anterior teeth of 
the majority of Mam¬ 
mals, the teeth of most 
Reptiles are replaced 
1 # CONICAL TOOTH OF AN 
irregularly and continu- extinct plesio- 
ously throughout life; saurian reptile. 
the successional teeth 
growing up beneath the bases of those in use, and gradually causing an absorp¬ 
tion of their roots. When teeth are distributed over the whole or a greater 
portion of the palate, they generally assume a more or less flattened and bean¬ 
like shape, so as to form a kind of pavement in the mouth, as shown in the 
accompanying figure of the under surface of the skull of an extinct reptile. 
UNDER SURFACE OF SKULL OF AN EXTINCT 
reptile (Cyamodus), with pavement - like 
TEETH ON THE PALATE. 
LEFT SIDE OF THE SKULL OF A BEAKED FLYING DRAGON (J liat. size). 
a, vacuity in front of the eye ; b, socket of the eye ; c, occipital spine ; d, angle of lower jaw ; e, extremity of 
upper, and e', of lower jaw ; q, articulation of the skull proper with the lower jaw ; s, point where the two branches 
of the lower jaw diverge.—After Marsh. 
Between conical and pavement - like teeth there are various intermediate grades, 
some of which will be referred to in the sequel. It is, however, by no means 
all members of the class that are provided with teeth; the tortoises and turtles 
being living examples of the total loss of these organs, and the consequent conver- 
