60 VENOMOUS SERPENTS. 



the Guaco may impart to the skin an odour which is repugnant 

 to the serpent and prevent it from biting. 



60. SERPENTS WITH MOVEABLE, VENOMOUS FANGS, are the most 

 formidable. The fangs, (Fig. 20, c.) situate in front of the 

 mouth, are isolated, very sharp, and pierced by a small canal, 

 which opens near their extremity ; they are fixed on very small 

 maxillary bones, (Fig. 18, im.) and these bones being supported 

 on a long pedicle, are very moveable, so that when the animal does 

 not wish to use them, they are folded backwards, and lie concealed 

 in a fold of the gum, and when required on the contrary, they 

 are erected. There is one of these long teeth on each side, and 

 behind each one, there are many germs to replace it, in the event 

 of its being broken in a wound ; but the intermaxillary bones 

 support no other teeth, and, consequently, we find in the upper 

 part of the mouth, only two rows of palatine teeth, instead of 

 four rows, as in Colubers. 



61. The head of these serpents is generally wide behind, and 

 their aspect is more fierce than that of the preceding. They are 

 all ova-viviparous, that is, they are born alive, because their eggs 

 are hatched before they are laid. Hence the name of Viper., 

 which is a contraction of viviparous, is given to most of them. 



62. The most remarkable genera of this division of venomous 

 Serpents, are the Crotalus, Triyonocephalus, Viper, and ]\aja. 



Fig. 21. 63. The RATTLE SNAKES, Cro- 



talus, owe their name to a sin- 

 gular apparatus which terminates 

 the tail, and which distinguishes 

 them from all other Ophidians. It 

 consists of a series of horny 

 scales, loosely fitting into each 

 other like a nest of boxes, which 

 move, vibrate and sound, when 

 the animal moves its tail, (Fig. 

 21.) The number of these scales 

 increases with age ; it seems there 

 is an additional one after each 

 moult, and that they are formed 

 by the epidermis of the Serpent, 

 turned upon itself like the finger 

 of a glove, and retained at the 

 extremity of the tail. This in- 

 strument vibrates with extreme 



RATTLE SNAKE. 



60. What are the peculiarities of the fangs, in venomous Serpents ? 



61. What is the origin of the name of Viper? 



62. What are the chief genera of the division of venomous Serpents ? 



63. What peculiarity gives name to the Rattle Snake? 



