32 GUIDE TO KEPTILES AND AMPHIBIANS. 



Mexico ; but the first has about 12 species, grouped in 4 genera, and 

 ranging over South and Tropical Africa. In the typical genus 

 Zonurus (426-427), the whole of the body and tail is encased in 

 bony plates, the horny coverings of which form sharp spines, especi- 

 ally on the tail. These Lizards inhabit desert districts. Specimens 

 of several species are exhibited in the case. 

 Case 20. The group of Lizards (family Anguidce) typified by the English 



" Slow- Worm " has a pleurodont dentition, with the teeth solid. 

 The tongue consists of two portions, of which the front half is 

 notched and capable of being withdrawn into the basal half. Bony 

 plates are developed in the skin of the body and head, and roof over 

 the temporal region of the skull. There is a marked tendency 



Fig. 34. 



The Slow- Worm (Angais fragilis) ; § nat. size. (No. 429-) 



throughout the family to a reduction of the limbs, culminating in 

 their complete loss in the Slow- Worm. Traces of the shoulder and 

 pelvic girdles always persist. The long, brittle tail is readily 

 replaced. All the species (40 or so in number, and arranged in 

 seven genera) are terrestrial and feed on animal substances ; and 

 some at least, like the Slow-Worm, produce living young. In the 

 American genus Gerrhonotus there is a pair of folds running along 

 the sides of the body, and the limbs are well developed. Similar 

 folds occur in the Glass-Snakes (Opliisaurm, 431), but the limbs are 

 represented only by a pair of flaps in the neighbourhood of the vent. 

 In the Slow-Worm (Anguis fragilis, 429,fig. 34) no external trace of 

 the fold or limbs remains : the notion that the creature is venomous 





