SERPENTS. 57 



These venomous teeth have been termed by naturalists moveable fangs, 

 but in fact it is the maxillary bone which moves; there are no other teeth 

 in it, so that in this kind of dangerous serpents only the two rows of 

 palatine teetli are to be seen in the upper part of the mouth. 



All the venomous species, whose mode of production has been accu- 

 racy determined, bring forth living young ones, as their eggs are 

 hatched without being laid, from which circumstance is derived their com- 

 mon name of Vipers, a contraction of viviparous. 



Venomous serpents with insulated fangs have external characters very 

 similar to those of the preceding ones, but in the greater number the jaws 

 are very dilatable, and the tongue very extensible. The posterior portion 

 of their head being broad, generally gives them a ferocious aspect, which 

 i.s a partial indication of their disposition. They form two great genera, 

 Crotalus and Vipera, the second of which has been variously sub- 

 divided, and some smaller ones group around them. 



Crotalus*', Lin. 



Rattlesnakes are celebrated above all other Serpents for the intensity of 

 their poison. Like the Boas, they have transverse simple plates under 

 the body and tail ; but their most distinguishing character is the rattle 

 which they carry at the end of the tail, and which is formed by several 

 scaly cornets loosely fitted into each other, and which move and produce 

 the peculiar noise or rattle whenever they crawl or shake their tail. The 

 number of these cornets increase with age, an additional one being always 

 found after each moult. There is a little round indentation or pit behind 

 each nostril']". All these species whose habitat is well ascertained are 

 from America. The danger resulting from the bite of these noxious 

 reptiles is in proportion to the warmth of the climate or of the season; 

 their natural disposition, however, is in general tranquil, and sufficiently 

 dull, and they are rather slow and heavy in their motions, never biting 

 unless provoked, or to kill the prey on which they feed. 



Although the Rattlesnake never ascends trees, its principal food con- 

 sists of birds, squirrels, ecc. It has long been supposed that it possesses 

 the faculty of rendering them powerless by its breath, or even of charming 

 them, that is to say, to force them by a single glance to drop into their 

 mouths; this, however, is not so, and the reptile in question seizes its 

 prey while under the agitation and terror produced by iis appearance J. 



In most of the species there are scales on the head similar to those mi 

 ih- back. 



('nil. horridus, L.; ; II, xli, (The Diamond Rattlesnake), 



io th pe i< mosl common in the United States; brown, with irre- 



* Crotalus, from the Greek word crotalon. 



•| Sue Russell and Home, Phil. Trans. 1804, pi. iii, p. 7'i. 



■ton, " Memoir on the Power of Fascination attributed to the I 

 snake," Philad. 17').;. 



