90 SIR JOSEPH FAYRER, K.C.S.I., ETC., 



circulation of mixed arterial and venous blood is regulated 

 by a heart, consisting of one ventricle, and two auricles. 

 Locomotion is effected in the terrestrial forms by the motion 

 of the numerous ribs, which are connected indirectly with 

 the abdominal scutee. These act as feet, and aided by the 

 undulations of the body, grasp the surface, thus effecting 

 the rapid movements of which a snake is capable. The 

 pelagic serpents swim like fish, motion being effected by the 

 undulations of the body and of the fin-like tail. 



Snakes have neither external ears nor eyelids ; the eye is 

 protected by a transparent capsule, which is shed with the 

 epidermis. The approach of moulting is indicated by 

 diminution in the brilliancy of the colouration, and a pearly 

 opacity of the eye ; the creature itself becoming more or 

 less apathetic until the process is completed. 



The scales and scutae form the basis of classification. 

 Those on the head are named as follows : — 



Rostral. 

 Anterior 



Posterior 



Vertical. 



Supra-ciliary 



Occipital. 



Nasals. 



Loreal. 



> Froutals. 



po?t } 0rbitals - 



J^P 61 '} Labials. 

 .Lower J 



Temporals. 



Mental. 



Chin-shields. 



The form and arrangement of the scales vary. In some 

 snakes they are plain and lie side by side, more or less 

 lanceolate in form. In others they are imbricated, that is 

 they overlap each other. On the head, in some snakes, they 

 are arranged as large plates or shields. On the abdomen in 

 the land snakes, they are in transverse plates for the purpose 

 of locomotion. In the JHydrophidae and burrowing land 

 snakes these are absent. 



Snakes are oviparous and viviparous; the colubrine, except 

 the pelagic forms, for the most part belong to the first class, 

 the viperine to the second. The cobra lays twenty to thirty 

 white, leathery eggs, which are hatched in some warm place 

 by natural heat. Some are said to incubate ; the python is 

 said to coil itself round the eggs until they are hatched. 

 The female of all snakes is said to be larger than the male ; 

 there are slight differences in colour and form, but no other 

 external distinction. 



Snakes hybernate in the cold, but returning warmth rouses 

 them into activity. They generally cat living creatures, but 



