20 INTRODUCTION 



with horn-like erect spines above the eyes or at the 

 end of the snout, which add greatly to their sinistral 

 appearance. 



The periodical shedding of the outer layer of the 

 epidermis in a single piece, including even the 

 covering of the eye, is one of the most striking 

 peculiarities of snakes, although paralleled in the 

 Lizards of the family Anguidae, to which our 

 British Slow-worm belongs. The skin becomes 

 detached at the lips, and is turned inside out 

 from head to tail, without any sort of laceration 

 when the snake is in good health. These exuviae are 

 transparent, but often carry a certain amount of 

 pigment, especially those of the Vipers, in which the 

 characteristic dark markings are perfectly visible ; 

 they usually exceed the length of the reptile, owing 

 to stretching. In Sea-snakes the epidermis is cast 

 piecemeal, and sloughing is a longer operation than 

 in ordinary snakes. 



In Rattlesnakes each piece of the rattle, or 

 " crotalon," in which the tail terminates, represents 

 a retained portion of the sloughed epidermis. This 

 remarkable appendage looks like a number of horny 

 rings, but it consists in reality of hollow, bell-like 

 pieces, similar to the terminal one, or "button," each 

 with a circular constriction, in which the incurved 

 free edge of the following piece fits, thus keeping the 

 pieces together without impairing the mobility 

 necessary to produce the rattling sound for which 



