80 ORGANS OF SUPPORT, 



is always slender in its middle, apart from the tibia, and 

 thickened at its ends. There are four bones of the tarsus, as 

 in the crocodiles, and the bones of the meta-tarsus like 

 those of the meta-carpus, and the phalanges of the toes and 

 fingers are lengthened to form prehensile flexible mem- 

 bers for climbing in these land forms of saurian rep- 

 tiles. 



The skeleton of the nilotic crocodiles (Fig. 41.) like that 

 of the gavials and alligators, belongs to reptiles destined to 

 swim through the water by the lateral movements of a 



FIG. 41. 



powerful muscular vertical tail, and also by the impulse of 

 long webbed feet. Their long bones are coarse in texture, 

 and filled internally with a loose osseous structure contain- 

 ing a thin oily marrow. The whole bones of the head are 

 firmly united together by sutures, so as to admit of no 

 motion on each other. The parietals are anchylosed to- 

 gether, the tympanic bone is fixed by sutures to the other 

 parts of the temporal, and forms a prominent condyle for 

 the lower jaw ; the median frontals are anchylosed together, 

 but the two anterior and the two posterior frontals are 

 detached. The large malar bones, continued from the 

 lachrymal to the temporals, form the outer boundary of the 

 orbits. The nasal bones extend between the upper jaw 

 bones to the intermaxillaries in the crocodiles and alligators ; 

 but in the gavials they extend only to a short distance 

 along the muzzle, so that that lengthened part of the face 

 is not weakened by so many sutures. The whole of the 

 rounded termination of the upper jaw is formed by the in- 

 termaxillaries which surround the nasal aperture. The teeth 

 of these crocodilian sauria are hollow striated cones, which 

 contain within their cavity the new teeth which are to 



