326 



CLASSIFICATION OF VERTEBRATES. 



which three species, C. horridus, C. adamanteus, and C. catenatus occur 

 in our eastern states. Agkistrodon contortrix, the copperhead, and A. 

 piscivorus, the moccasin, lack the rattle, as does Bothrops lanceotatus, the 

 fer-de-lance of the Antilles, possibly the most deadly snake. 



SECTION IV. TORTRICINA. Colubriform snakes with supratem- 

 poral articulated with bones of skull; mouth incapable of distention ; a 

 horizontal maxillary bone, rudiments of pelvis and anal claw. The species, 

 belonging to Tortrix, Rhinophis, Uropeltes, etc., are all tropical. 



SECTION V. OPODERODONTA. With articulated supratemporal, 

 rudimentary pelvis, head and eyes small ; bones of skull immovable ; mouth 

 incapable of distention, teeth in only upper or under jaw, body worm-like, 

 tail very short. Seventy species in the tropics, where they live a burrowing 

 life like earthworms. Typhlops ; Stenostoma. 



ORDER VIII. CROCODILIA (LORICATA, CATAPHRACTA). 



Lizard-shaped reptiles with bony, dermal scutes ; bicipital 

 ribs ; a supra- and usually an infratemporal fossa ; teeth in alve- 

 oli in the edges of the jaws only ; quadrate immovable ; sternum 

 and episternum present ; four, usually clawed, ambulatory limbs ; 

 tail long, keeled ; lungs compound sacs ; vent longitudinal ; penis 

 unpaired; heart with ventricles completely separated. 



FlG. 321. Skull of alligator, an, angulare ; ar, articulare ; bo, basioccipital ; 

 bs, basisphenoid ; d, dentary ; /;-, frontal ; _/, jugal ; /, lachrymal ; ///JT, maxillary ; 

 ptn, premaxillary ; pt, pterygoid ; y, quadrate ; <//', quadratojugal ; tr, os transversum. 



The crocodiles, alligators, and caimans, and their extinct rel- 

 atives, are sharply marked off from all other reptilian groups, 



