CROCODILES AND CAIMANS— LIZARDS 



409 



Another type of eyelid is presented by C. palpebro&us, in which it is flat and 

 entirely bony, the bone consisting of four separate pieces. 



An imperfectly known caiman from the Magdalena River, Colombia, on 

 account of certain alleged structural peculiarities, has been made the type of a 

 distinct genus under the name of Perosuchus fuscus. 



In general habits caimans are very similar to crocodiles and alligators. 



Of lizards, one species (Heloderma horridum) of the family 

 Helodermatidce is a native of Mexico; the other, commonly known as 

 the Gila monster (H. suspectum), inhabiting the deserts of Arizona, These lizards, 

 which are poisonous, are very brilliantly coloured — orange or red with black 

 markings; and, although it has been stated that this colouring harmonises with 

 the colour of the sand on which these reptiles delight to bask, it is more probably 





Lizards. 



o < ^Vt 



HELODERMA 



of the " warning " type, that is to say, it serves to proclaim the dangerous nature 

 of these lizards. 



Considerable difference of opinion has been expressed in regard to the character 

 of the bite of these lizards, some naturalists maintaining that it is more or less 

 completely innocuous, while others state that it is intensel} 7 poisonous. As regards 

 frogs, mice, rabbits, dogs, pigeons, poultry, etc., experiments leave no doubt that 

 the fangs are venomous. As regards the effects on the human subject, a statement 

 was made in 1882 to the effect that a bite in the thumb by a Gila monster was, 

 after severe local pain, followed only by great weakness and perspiration. On the 

 other hand, in 1888, a case was cited in which death is stated to have occurred a 

 few hours after the infliction of the bite ; this being the third or fourth case of a 

 fatal result attending the bite of these lizards in Arizona. In 1911 a lady was bitten 

 in the index finger of her right hand while holding a Gila monster. By prising open 



