CROCODILES. 3 



Lizard together, and associate the Slowworm with the Snake ; 

 whilst a study of their internal structure shows the Lizard and the 

 Slowworm to be most closely related to each other, and both 

 nearer to the Snake than to the Crocodile. 



Reptiles are most abundant in hot climates, became less nume- 

 rous in higher latitudes, and are altogether absent in the Arctic 

 and Antarctic regions. 



In the Gallery — 



Wall-Cases 1- 9 contain the Crocodilians. 



Large specimens are exhibited separately on stands placed on the 

 floor of the Gallery. 



Order I. CROCODILIA. 



The Crocodilians diflFer in many anatomical characters from 

 the LacertilianSj or true Lizards, with which they were formerly 

 associated on account of their external resemblance. The organs 

 of their chest and abdomen are separated from each other by 

 a muscular diaphragm ; their heart is divided into four cavities, 

 as in the higher vertebrates. The ribs are provided with two 

 heads for the articulation with the vertebrae, and with processes 

 directed backwards; and their abdomen is protected by a series of 

 transverse bones, as may be seen in the skeletons of the Gavial 

 and Crocodile (opposite Wall-Cases 4-9). The teeth are implanted 

 in sockets, while in other recent Reptiles they are grown to the bone 

 of the jaws. The tongue is completely adherent to the floor of the 

 mouth. The nostrils are situated close together on the upper side 

 of the extreimity of the snout ; the eyes and the ears likewise are near 

 to the upper profile of the head, so that the animal can breathe, see, 

 and hear whilst its body is immersed in the water, the upper part 

 of the head only being raised above the surface. When it dives, the 

 nostrils are closed by valves, a transparent membrane is drawn over 

 the eye, and the ear, which is a horizontal slit, is shut up by a 

 movable projecting flap of the skin. The limbs are weak, the ante- 



