REPTILIA. 441 
noticed in the skate, have been more fully described in 
the chick, p. 380.) 
Again, the reptiles have twelve cranial nerves, the spinal 
accessory and hypoglossal being added to the ten of 
Amphibia. and the skeleton is much more completely ossi- 
fied than is the case in the latter. The body is usually 
protected in an exoskeleton of scales or scutes, which is 
either purely epidermic and cuticular in nature, or is dermal 
and formed of bony tissue 
In the skeleton the reptiles have the typical pentadactyle limbs and 
the ankle-joint is intertarsal. The shoulder-girdle usually has clavicles 
and episternum as well as the three primary bones—the precoracoid, 
coracoid and scapula. In the pelvic-girdle the ilium usually fuses with 
two sacral vertebree and there are usually epipubic bones. There are 
often a number of membrane-bones called abdominal ribs. In the skull 
the quadrate suspends the lower jaw which is composed of several 
bones ; the teeth are polyphyodont and homodont and are attached to 
the surface of the bone (acrodont) or at the side (pleurodont), and they 
may occur on the palatines, pterygoids and vomers, as well as the 
premaxillz, maxilla and dentary. The skull has a single occipital 
condyle, formed largely by the basioccipital but partly by the ex- 
occipitals, and the facial portion of the skull is much larger and broader 
than the cranial. There is often a peculiar ¢ransverse bone connecting 
the maxilla and the pterygoid. There is only one ear-ossicle, the 
columella auris. 
Most of the reptiles resemble the amphibians in the 
three-chambered heart, the three complete aortic arches and 
the condition of the circulatory system. 
ORDER I.—Rhynchocephalia. 
Sphenodon (or the New Zealand Lizard) is a lizard-like 
animal, found in New Zealand, possessing a series of 
primitive structural peculiarities which lead zoologists to 
place it in an order by itself. The principal of these are the 
amphiccelous vertebre, the presence of intercentral elements 
between the vertebree and of teeth on the palatines and 
vomers (young). 
OrDER II.—Lacertilia. 
The lizards have an exoskeleton of horny epidermic 
scales which are periodically shed. Most have two pairs of 
walking limbs and a long tail. The teeth are either fused 
