RATTLESNAKES. 77 



struck by one of these reptiles, died in a few hours. Its motions 

 are sluggish, and when approached it assumes a threatening aspect, 

 raising its head and darting out its tongue. It chiefly occurs in 

 pastures and low meadow grounds, where it feeds on field-mice, 

 frogs, and the smaller disabled birds." The poison of the Black 

 Water Viper is equally to be dreaded. 



The true Rattlesnakes have the tail furnished with the extra- 

 ordinary appendages at its tip which will be described presently. 

 According to differences in the shields and scales covering the 

 head, Dr. Gray arranged them into three genera Crotalophorus, 

 with three species ; Uropsophus, with one ; and Crotalus also 

 with one, C. horridus^ which appears to be the only one known in 

 South America. Of the Common Northern Rattlesnake (Uro- 

 psophus durissus), Dekay remarks that, " Although furnished with 

 such deadly weapons, the rattlesnake can scarcely be termed a 

 vicious animal, for he rarely strikes unless almost trodden upon. 

 When suddenly disturbed, he throws himself into a coil, and warns 

 the aggressor by rapidly vibrating his rattles, which, however, can 

 scarcely be heard beyond the distance of a few yards. This is most 

 usually the case, but they occasionally strike without the slightest 

 warning. At the moment the snake strikes, he ejects the venom 

 forcibly into the wound. In an instance of a very large rattlesnake 

 from Florida (C. horridus\ which was irritated, he struck violently 

 against the iron wire on the side of the cage, and spurted the venom 

 to the distance of three feet."* The fibulae, or rattles, seldom exceed 

 fifteen in number, and are rarely so many. 



The Common Northern Rattlesnake (Uropsophus durissus, Fig. 

 19) sometimes attains to six feet in length, the middle being about 

 the size of a man's leg ; t the colour of the back is grey, mixed with 

 yellow. Upon this foundation extends a longitudinal row of black 

 spots, bordered with white ; towards the muzzle the flat head is 

 covered with six scales larger than the others, and disposed in three 

 transverse rows, each formed of two scales. The males are smaller, 

 much more brightly and markedly coloured than the other sex. 

 The very long and visible fangs are situated in front of the upper 

 jaw. The scales on the back are oval, and raised in the middle by 

 a bone which extends in the direction of their greatest diameter. 



* We have seen a Cobra thus spurt its venom against the plate-glass cover of 

 the box in which it was kept. ED. 



f That the Timber Rattlesnake of the United States sometimes grows to the 

 length of seven or eight feet we have no doubt j the Prairie Rattlesnake, however., 

 seldom exceeds two feet. ED. 



