584 



REPTILES. 



The tail is laterally compressed and assists in swimming 



Teeth occur in distinct sockets 

 in the premaxillce, maxillce, 

 and detztaries. 



In modern Crocodilians, al 

 most all the vertebra are pro- 

 ccelotis. 



The skull has many char- 

 acteristic features, such as the 

 unio?i of maxilla:, palatines, 

 and pterygoids iji the middle 

 title oti the roof of the mouth, 

 a/id the consequent shunting of 

 the posterior nares to the very 

 back of the mouth. 



Some of the ribs have double 

 articulating heads, and bear 

 small uncinate processes some- 

 what like those of birds ; trans- 

 verse ossif cations associated 

 with the subcutaneous fibrous 

 tissue of the abdomen from so- 

 called abdominal ribs. 



The heart is four chainbered ; 

 a muscular diaphragm par- 

 tially separates the thoracic 

 from the abdomitial cavity. 



The cloaca has a longitudinal opening 

 a grooved penis. 



The Crocodilians are oviparous. The eggs have firm cal- 

 careous shells, atid are laid in holes in the ground. 



Fig. 201. — Lower surface of 

 skull of a young Crocodile. 



P.insc.. Premaxilla ; wj-., maxilla; 

 o.t.^ OS transversum ; 

 /., juga] ; (P.y., quad- 

 quadrate : /.«., pos- 

 , cond;-le. 



The males have 



pal. , palatine ; 

 //. , pter^-goid ; 

 ratu-jugal ; Q.^ 

 terior nares ; c. 



Some of the Charadeiistic Features in tlie Skeletal .System of 

 Croeodiliaus. 



(These notes on the skeleton are in great part taken from Hu.xley's 

 Manual.) 



Numerous transverse rows of sculptured bony plates or scutes, ossified 

 in the dermis, form a dorsal shield. On the ventral surface the scutes 

 are absent, except in some alligators, in which they are partially ossified. 

 But besides and above the scutes, there are horny epidermic scales like 

 those in other Reptiles. The hide is often used as leather. 



The vertebral column consists of distinct cervical, dorsal, lumbar, 



