ORDER OPHIDIA. 337 



naturalists have employed themselves in making researches 

 on the anatomy, the manners, and the poison of these reptiles, 

 and accordingly their history is now tolerably well-known. 



The head of the crotali is broad, triangular, and generally 

 flatted in its entire extent. The scales of the cap of the 

 cranium, and of all that part which is between the eyes 

 and beyond them, are similar to those of the back ; but 

 those of the muzzle and those which cover the eyes, are 

 often larger and in the form of plates. The muzzle is hol- 

 lowed with a small rounded fosset behind each nostril. 



Their eyes are exceedingly brilliant and provided with a 

 nictitating membrane. 



The mouth is very large ; the tongue, forked at its extre- 

 mity, is partly enclosed in a thin sheath, and susceptible of 

 prompt movements in different directions. The symphysis of 

 the lower jaw is not soldered, and the bone is armed with 

 crooked teeth, which diminish in length in proportion as they 

 recede from the muzzle. Enough has been said already 

 respecting the nature of the venomous fangs, &c. 



The body is robust, elongated, cylindrical, covered above 

 with carinated scales, all of which are pvit in motion by a 

 peculiar muscle ; the anus is simple and transverse. 



The tail is short, cylindrical, and somewhat thick. The 

 number of little bells which terminate it, increase with age ; 

 and an additional one is formed at every moulting or casting 

 of the skin. These bells are truncated quadrangular pyra- 

 mids, broader in one direction than another, and received 

 within each other in such a manner that only the third part 

 of each is visible. They are hollow bones, and have each 

 a rigid epiphysis united to them, though it is only appa- 

 rent in the last or terminal bone. Thus the tip of every 

 uppermost bone runs within two of the bones below it. Thus 

 the bells are held without being actually bound together, and 



VOL. TX. z 



