LACERTILIA. 



343 



with the tibia and fibula in a way which allows of very little 

 motion. The distal row contains a cuboid carrying the meta- 

 tarsals of the fourth and fifth digits, that of the fifth being bent 

 as in Chelonia. Other distal tarsals may be present or they 

 may be fused with the metatarsals. 



The phalangeal formula of the maiius is usually 2. 3. 4. 5. 3, 

 of the pes 2. 3. 4. 5. 4. 



Alimentary canal. Teeth are present on the premaxillae, 

 maxillae, and dentary, and often on the palate. They may be 

 conical, blade-like, or crushing (Cyclodus). They usually become 

 ankylosed to the bone, either by 

 their bases to the edge of the jaw 

 (acrodont), or by their sides just 

 inside the edge (pleurodont). They 

 are never lodged in alveoli (the- 

 codont). The tongue varies con- 

 siderably. It is generally notched 

 anteriorly and posteriorly drawn 

 out into two processes which may 

 unite behind the glottis, so that 

 the glottis lies in the back of the 

 tongue. In the geckos, Iguanidae, 

 Agamidae, etc., it is short ; in 

 the Amphisbaenidae, it is forked. 

 In some forms (Varanidae, etc.) 

 it is long, narrow and forked, 

 and provided with a sheath at 

 its base into which it can be 

 retracted. In the chameleons 

 it is very long and clubbed at its 

 end. 



Salivary glands are absent, but labial glands opening on the 

 lips are present. There is a gall-bladder, usually a short caecum 

 on the anterior end of the rectum, and the cloaca has a bladder. 



The larynx consists of a cricothyroid cartilage and of arytenoid 

 cartilages. The cricothyroid frequently has fontanelles and in 

 Amphisbaenidae is represented by two lateral bands of cartilage 

 united by cross bands (as in snakes). An epiglottis is some- 

 times present. Vocal chords are absent except in geckos and 

 chameleons. The tracheal rings are usually complete. The 



Fm. 188. Ventral view of the pectoral 

 girdle and sternum of Iguana. Letters 

 as in Fig. 187 (from Huxley). 



