CROCODILES. 3 



naturalists of the last and preceding centuries, is guided by external 

 appearance only, would without hesitation place the Crocodile and 

 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 

 uearer to the Snake than to the Crocodile. 



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

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



Large specimens are exhibited separately on stands placed on the 

 floor of the Gallery. 



Order I. CROCODILIA. 



The Crocodilians differ in many anatomical characters from [Cases 

 the Lacertilians, or true Lizards, with which they were formerly 1_i ^-J 

 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 skeleton of the large Cro- 

 codile (CaseE, opposite Wall-Case 5). The teeth are implanted in 

 sockets, while in other recent Reptiles they are united to the jaws. 

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

 nostrils are situated close together at the upper side of the extre- 

 mity 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 



