6 REPTILE GALLERY. 



the Tuatera from ordinary Lizards; but important diflferences 

 obtain in the structure of its skeleton, viz. the presence of a double 

 horizontal bar across the temporal region, the firm connection of 

 the quadrate bone with the skull and pterygoid bones, biconcave 

 vertebrae (as in Geckos and many fossil Crocodilians), the presence 

 of a plastron formed of numerous small bones and of uncinate 

 processes to the ribs (as in Birds and Crocodiles). 



Order III. LACERTILIA, or Lizards. 



Cases The Order of Lizards comprises over 1900 species, whicli 



]0-l/.] exhibit a great variety of form and structure. Some, like our 

 common Lizards, possess four legs and a long tail, and are 

 endowed with great rapidity of motion ; others, like the Chamse- 

 leons, are arboreal, and have their limbs and tail adapted for climb- 

 ing on the branches of trees ; others, like the Geckos, can ascend 

 smooth vertical surfaces, their toes being provided with specia! 

 adhesive organs. The limbs may be rudimentary or disappear 

 entirely, as in our common Slowworm, in which case the Lizard 

 assumes the appearance of a Snake ; but, in all, rudiments at least of 

 both pectoral and pelvic bones are hidden under the skin. Lizards 



Fi-. 2. 



Hind legs of Lizards, to show the gradual abortion. 



Chalcides ocellatvs ; b, Chalcides mionecton ; c, Chalcides tridactylvs ; 

 d, Lygosoma lineo-punctulutum ; e, Chalcides guentheri. 



