5 36 LACERTAE chap. 



down. On cool and dull days they do not appear at all, and 

 during part of the cooler season they require artificial heat until 

 they are ready to hibernate. Unless they are allowed to hiber- 

 nate, they will keep ' on feeding through the winter, but in that 

 case are sm-e to die in the following spring. 



Fam. 3. Xenosauridae, with Xenosaurus grandis in Southern 

 Mexico as the sole species, seems to connect the Iguanidae with 

 the Anguidae. According to Boulenger, its affinity to the 

 former is shown by the T-shaped interclavicle, the absence of 

 symmetrical bony shields on the head and of osteodermal plates 

 on the body. Affinity to the Anguidae is indicated first by the 

 short tongue, which has a narrow, feebly incised, retractile 

 anterior part, covered with flat papillae ; secondly, by the teeth, 

 which, instead of being hollow at the base, are solid ; lastly, by 

 the palatine bones, which are widely separated. 



X. grandis, scarcely one foot in length. The body is de- 

 pressed, covered above with minute granules and tubercles, below 

 with smooth scales. A distinct fold of skin extends from the 

 axilla to the groin, recalling the more strongly developed lateral 

 fold of some of the Anguidae. 



Fam. 4. Zonuridae. — This family, comprising four genera 

 with about one dozen species in South and Tropical Africa, and 

 in Madagascar, likewise seems to connect Iguanidae and An- 

 guidae. It is distinguished from the former by dermal ossifica- 

 tions, which roof over the supratemporal fossa ; from the latter 

 by the tongue, the hollow teeth, and, in Zonurus at least, by the 

 occurrence of dermal ossifications on the trunk and tail. The 

 tongue is short, villose, scarcely protractile, entire, or but feebly 

 nicked at the tip. The Zonuridae may therefore be defined as 

 phurodont African lizards with a short tongue, and with a bony 

 roof to the supratemporal fossae. 



Zonurus. — The whole head, back, and tail are covered with 

 bony scales, the horny covering of which forms very sharp spikes, 

 especially on the tail. The body is depressed. The ear-opening 

 is large. South Africa, in dry and rocky localities ; one species, 

 Z. tropidosternum, in Madagascar. • 



Z. giganteus s. derhianus, with strong spikes on the occiput, 

 neck, and tail. General colour yellowish brown. Total length 

 about 15 inches. 



Chamaesaura of South Africa closely approaches the An- 



