3i8 



SNAKES. 



about the nose and mouth, exceptions which are now and 

 then found in non-venomous ones also. The preceding three 

 illustrations are the head shields of a Colubrine snake, in 

 which a greater uniformity prevails. Below are given four 

 other types, though even here variations are constantly 



occurrmg. 



Fig. a. One of the Indian Crotalidce. It has two con- 

 spicuous supraciliary shields, two equally conspicuous 

 anterior frontals over the nostril. The rest are small, and 

 those on the top are absent altogether. The scales are all 

 finely carinated. 



Fig. b. The head of a Colubrine snake in which the 

 same scales appear as those in Fig. i of the preceding 

 page, viz. two orbitals, etc., but are all much smaller, and 

 do not therefore more than half cover the head. 



Fig. c. The head of a sea snake, which as to design 

 is really pretty, and, as Giinther affirms, so different 

 from land snakes in respect to head shields, that without 

 any further investigation an ophiologist can at once dis- 

 tinguish the JiydropJiidcB. 



Fig. d. The head of a viper in which only very small supra- 

 ciliary and nasal (or anterior frontal) shields are seen. The 



