KEPTILES. 295 



b. Hind-head destitute of a hood. 



aa. Furnished with cuticular appendices on the forehead. 



57. CERASTES. Scales on the head similar to those on 

 the back. C. vulgaris. 



bb. Fore-head destitute of appendices. 

 Head covered with small plates. 



58. CHERSEA. Aesping. Head covered in the middle 

 with three plates. C. vulgaris. 



59- HBMACHATUS. Head covered with four rows of 

 large plates, H. vulgaris. 



Head covered with common scales. 



60. COBRA. Scales on the head carinated. The head 

 itself, from the eyes to the snout, subtriangular. C. atropos. 



61. VIPERA. Viper. Scales on the head rough. V. 

 Berus. Common viper or adder. 



b. Head, behind, of the same size as the neck. 



This uncommon narrowness of the head arises from the 

 shortness of the os quadrature, and the osseous peduncle 

 by which it is '.united with the skull. The power of swal- 

 lowing large objects is consequently limited, as the jaws 

 have but little motion. 



62. ELAPS. Head covered with large plates. E.lac- 

 *eus. Milky viper. 



B, Tail compressed. 



63. PEATURUS. Head covered with large plates. P. 

 laticaudatus. 



hood. This motion is produced by the cuticular muscles of the neck aided 

 by the moveable ribs. This mechanism, as displayed in the common cobra 

 di capello, is exhibited by Sir EVZRARD HOME, in his " Lectures on Compa- 

 rative Anatomy," vol. II. tab. ii. iii. iv. 



