RATTLESNAKES. 83 



Field-mice, Frogs, and the smaller disabled birds." The poison 

 of the black Water Yiper is equally to be dreaded. 



The true Rattlesnakes have the tail furnished with the extraor- 

 dinary 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 (Urop- 

 sophus 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 Rattle- 

 snake 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 sometimes attains to six feet 

 in length, the middle being about the size of a man's leg ; the 

 colour of the back is grey, mixed with yellow. Upon this foun- 

 dation 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 less darkly 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. The underpart 

 of the body is furnished with a single row of large plates. The 

 Rattlesnake owes its name to a remarkable peculiarity in its struc- 

 ture ; the extremity of the tail is furnished with small horny cells, 



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

 box in \vhich it was kept. ED. 



G2 



