312 ZOOLOGY SECT. 



ribs have simple vertebral extremities. The quadrate is movably 

 articulated with the skull. There is no inferior temporal arch. 

 The nasal apertures of the skull are separate. The limbs, when 

 present, are sometimes adapted for terrestrial locomotion (Lacer- 

 tilia), sometimes for swimming (Pythonomorpha). The teeth are 

 acrodont or pleurodont (see below). The lungs are simple sacs. 

 There is always a wide cleft between the right and left divisions 

 of the ventricular cavity. The optic lobes are approximated, and 

 the cerebellum is extremely small. 



Sul-Order a. Lacertilia. 



Squamata in which, as a rule, the limbs are present and are 

 adapted for walking. The mouth is capable of being opened to 

 only a moderate extent. The maxillae, palatines, and pterygoids 

 are incapable of free movement. The rami of the mandible are 

 firmly united at the symphysis. There are nearly always movable 

 eyelids and a tympanum. A sternum and an episternum are 

 present. 



Including all the Lizards, such as the Skincs, Geckos, Monitors, 

 Iguanas, Amphisbsenians, Chamaeleons, and other groups. 



Sub-Order b. Ophidia. 



Squamata with long narrow body, devoid of limbs. The mouth 

 is capable of being opened to form a relatively very wide gape by 

 the divarication of the jaws. The maxillae, palatines, and ptery- 

 goids are capable of free movement. The rami of the mandible 

 are connected together only by elastic fibres at the symphysis, so 

 that they are capable of being widely separated. There is no 

 separate supra-temporal ossification. Sternum and episternum 

 are absent. Movable eyelids and tympanum are absent. 



Including all the Snakes Vipers, Rattlesnakes, Sea-Snakes, 

 Fresh-water Snakes, Tree-Snakes, Blind-Snakes, Pythons, and 

 Boas. 



Siib-Order c. PytJionomcrpha. 



Extinct Squamata with elongated Snake-like body, provided 

 with limbs which take the form of swimming-paddles. The 

 skull resembles that of the Lacertilia; a supra-temporal -helps to 

 suspend the quadrate. The union of the rami of the mandible 

 was ligamentous. There is, as a rule, no sacrum, the ilia not 

 articulating with the spinal column. 



ORDER II. RHYNCHOCEPHALIA. 



Lizard-like, scaly Reptiles with well-developed pentadactyle 

 limbs adapted for walking. The opening of the cloaca is trans- 

 verse. There are no copulatory sacs. The vertebrae are amphi- 

 erelous, sometimes enclosing vestiges of the notochord. The 



