504 ZOOLOGY. 



ten days, the skin finally separating from the spines of tne 

 head and the claws. (Hoffman.) 



Our most common lizard in the Middle and Southern 

 States is Sceloporus undulatus Harlan (Fig. 440). it is 

 common, running up trees. The iguanas are very large liz- 

 ards inhabiting the "West Indies and Central America ; the 

 head is protected by numerous small shields, with a dorsal row 

 of bristling spines. They are about three feet long, live in 

 the lower branches of trees, and are said to be excellent eat- 

 ing. A still larger form, closely resembling the iguanas, is 

 the sea-lizard (Amblyrhynclms) of the Galapagos Islands, 

 where it lives in the rocks by the shore, feeding on seaweeds. 

 These large creatures are among the largest of existing liz- 



Fig. 443. Tongue of Chameleon. Natural size. After Rymer Jones. 



ards, being eighty-five centimetres (over 3 feet) in length. 

 Closely allied to the iguanas were a number of extinct sau- 

 rians of colossal size which flourished in the Jura-Trias and 

 Chalk Periods. 



The largest lizard in Mexico is the Heloderma horridum 

 of Wiegmann. It grows to the length of one metre (over 

 three feet). It is allied to the iguanas, but the body is 

 heavily tuberculated. Heloderma suspectum Cope, inhab- 

 its southern Utah, Arizona, and New Mexico. The largest 

 of the existing lizards are the monitors, or species of Vara- 

 nus, of tropical rivers, which nearly rival the crocodiles in 

 size, being five or six feet in length. 



Order 4. Chelonia. Although the tortoises and turtles 

 are a well circumscribed group, with no aberrant or connect- 



