CROTALUS DURISSUS. 55 



numbers, and they are now almost extirpated in the neighbourhood 

 of large towns. None are said to be found farther north than the 

 mountains near Lake Champlain, but they infest South America 

 even as far as Brasil. Rattle- snakes delight in woods and lofty 

 hills, especially where the strata are rocky or chalky. There are at 

 least three well characterised species, viz., Crotalus durissus, 

 C. horridus, C. miliarias; and a fourth, C. cascahella, has lately 

 heen discovered by M. Spix, in Brasil. 



The species here represented inhabits the warmer parts of North 

 America, as far as the 45th degree of latitude. It is from 

 four to six feet in length, and the thickness of a man's 

 arm. The general colour is of a deep brown above, and marked 

 along the back with a row of dark brown or nearly black lozenge- 

 shaped spots, bordered with pale brownish yellow. On the upper 

 part of the neck are three or four blackish lines. The head is large 

 and flat, of a triangular shape, and covered with scales similar to 

 those on the back ; but those on the muzzle, and those which 

 cover the eyes, are larger, and in the form of plates. The rostrum 

 is obtuse and truncated ; and there is a small rounded fosset 

 behind each nostril. The scales of the back are carinated, of an 

 oblong oval form ; those of the lateral row, immediately above the 

 abdominal scuta, broader and somewhat rhomboidal. The shields 

 are entire on the belly and below the vent. The opening of the 

 mouth is wide, and in the upper jaw, on each side, is armed with 

 crooked teeth, which diminish in size in proportion as they recede 

 from the muzzle. The eyes are large, exceedingly brilliant, and 

 furnished with a nictitating membrane. The tail is rather thick, 

 and furnished with a dark brown coloured rattle. 



To Thomas Bell, Esq. F. R. S., New Broad Street, I am in- 

 debted for the fine specimen from which the drawing on the an- 

 nexed plate was made, and who, with the frank liberality that cha- 

 racterises a mind ardent in the pursuit and advancement of science, 

 has allowed me the use of his splendid collection of this department 

 of natural history. — Fig. 1 exhibits the under side of the head ; 

 2, the upper side of the head ; 3, a section of the rattle. 



From a paper published many years ago, in the Philosophical 

 Transactions, by Dr. Tyson, on the anatomy of the Rattle-snake, 



