586 



REPTILES. 



They form seven transverse 



under the skin and above the muscles, 

 series, each composed of several ossicles. 



As to the skull, there is an interorbital septum with large alisphenoids ; 

 the presphenoid and orbitosphenoids are at best incompletely ossified ; 

 all the bones are firmly united by 

 persistent sutures ; both upper 

 and lower temporal arcades are 

 completely ossified ; the maxillae, 

 the palatines, and the pterygoid, 

 meet in the middle line of the 

 roof of the mouth, covering the 

 vomers, and determining the 

 position of the posterior nares 

 at the very back of the mouth ; 

 an os transversum extends be- 

 tween the maxilla and the junc- 

 tion of palatine and pterygoid ; 

 an epi-pterygoid runs down from 

 post-frontal to os transversum ; 

 the quadrate is large and immov- 

 able ; there are large parotic 

 processes ; the tympanic cavity 

 is completely bounded by bone ; 

 the teeth, which are borne by 



FIG. 203. Half of the 

 girdle of a young Crocodile. 



pelvic 



//., Ilium ; a.f., acetabulum ; 7s,, 



ischium ; /*., pubis. 

 premaxillae, maxillae, and den- 

 taries, are lodged in distinct cavities ; beside and eventually beneath 

 the teeth lie reserve "germs" of others. 



Each ramus of the mandible consists, as in most Reptiles, of a cartilage- 

 bone the articular working on the quadrate, and five membrane bones 

 dentary, splenial, coronoid, angular, and surangular. 



The hyoid region is very simple. 



In the pectoral arch there are no clavicles nor epicoracoids, but 

 there is a so-called interclavicle or episternum ; the fore limb is well 

 though not strongly developed ; there are five digits, webbed and 

 clawed. 



In the pelvic arch, large ilia are united to the strong ribs of the two 

 sacral vertebrae ; the pubes slope forward and inward and have a cartila- 

 ginous symphysis ; the ischia slope backward and have a symphysis ; 

 ilia and ischia form almost the whole of the acetabulum. The hind- 

 limbs bear four digits, webbed and clawed. 



Some of the Characteristics of the various organs of Crocodilians. 



The Crocodilians are seen to best advantage in the water, swimming 

 by powerful tail strokes. The limbs are too weak for very effective 

 locomotion on land, the body drags on the ground, and the animals are 

 stiff necked. Although many, especially in their youth, feed on fishes 

 and small animals, the larger forms lurk by the edge of the water, lying 

 in wait for mammals of considerable size. These they grasp in their 

 extremely powerful jaws, and drown by holding them under water. If 

 the dead booty cannot be readily torn, it is often buried and left until it 



