620 REPTILIA. 
processes, as in Birds ; as in crocodiles, there are numerous ‘‘ abdominal 
ribs,” ossifications in the subcutaneous fibrous tissue of the abdomen. 
The anterior end of the ‘‘ plastron” thus formed overlaps the posterior 
end of the sternum. The inner ends of the clavicle rest on a median 
episternum (interclavicle). ; . 
The pineal or parietal eye, which reaches the skin on the top of the 
head, is less degenerate than in other animals, retaining, for instance, 
distinct traces of a complex retina, 
Near the living Sphenodon, 
the Permian Palgohatteria, the 
Triassic Myperodapedon, and 
some other important types may 
be ranked. Along with these 
may be included the remarkable 
Proterosaurus from the Pérmian, 
though Seeley establishes for it 
a special order—Proterosauria, 
as distinguished from Rhyncho- 
“cephalia. According to Baur, 
quoted by Nicholson and 
Lydekker, ‘‘the Rhyncho- 
cephalia, together with the 
Proterosauria, to which they 
are closely allied, are certainly 
the most generalised group of 
all Reptiles, and come nearest, 
in many respects, to that order 
of Reptiles from which all others. 
took their origin.” 
Order LacerTILia 
Lizards 
GENERAL CHARACTERS. 
—The body ts usually well 
stoniant covered with scales. In 
BH., Body of the hyoid (basihyal) ; mast, both fore- and hind- 
#., representing another part of the limbs are developed ana 
pyle orehs Ae? Beco: = Dear clawed digits, but either 
arch; P.C., posterior cot repre- pair or both pairs may be 
senting the second branchial arch. absent. The pec toral and 
pelvic girdles are always present, in rudiment at least. 
There is a sternum and a V-shaped episternum. Unlike 
snakes, lizards have non-expansible mouths. The maxilla,, 
palatines, and plerygoids are fixed, and there is usually 
a mandibular symphysis. There are almost always 
Fic. 338.—Hyoid apparatus of a 
