5294 PHILOSOPHY OF ZOOLOGY. 



50. Caudisona. Rattle-snake. The head in this genus 

 (the title of which is derived from the old trivial name of 

 this most remarkable species), is covered with scales simi- 

 lar to those on the back. C. horrida. Boquira. 



51. Crotalus. Millet. Head covered with large plates. 

 C. vnliaris. 



Tail destitute of a rattle. 



52. Scytalus. Destitute of nasal bags. The species 

 of this genus, natives of India, are but imperfectly 

 known. 



b. The entire shields under the tail not continued to the 

 extremity. 



53. Acanthophis. Shields double towards the extre- 

 mity of the tail, which terminates in a spinous process. 

 There are two species, A. palpcbrosus, and A. Brownii. 



54. Langaia. Shields behind the vent, forming rings 

 which surround the body. The under side of the tail to- 

 wards the extremity, covered with small scales. Snout 

 produced. L. nasuta. 



Shields behind the vent divided. 

 A. Tail round. 



a. Head behind larger than the neck. 

 Head furnished with crumens. 



55. Tkigonocephalus. Head much enlarged behind. 

 Tail frequently armed with a spinous process. T. lanceo- 

 latits. 



Destitute of crumens. 



(a.) Hind-liead furnished with a hood. 



56. Naja. Head covered with large plates. A^. lutcs- 

 cens *. 



• When the animals of this gioup are irritated, the skin on the neck is 



expanded and drawn forwards, and ;ippcars behind the head as a kind of 



