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JOURNAL, R.A.S. (CEYLON). [VOL. XI. 



the parts of animals considered separately : in fact, the grada- 

 tions in form would be perfect from any known snake to 

 any other, from the little worm-like burrower to the oar-tailed 

 sea-snake. There is a Tropidonotus (Nos. 29 to 32) that shows 

 such an inclination to develop the hood of the cobra that 

 it suffers largely by its resemblance.* But these tables are 

 only concerned with facts as they exist : when a type can be 

 defined it is represented by a letter ; when it cannot, the 

 letter stands for a combination of useful characters. 



Ventrals and Sub-Caudals. 



Besides the form, the other characters used in the diagnosis 

 of snakes are the scales, mouth, nostrils, eyes, teeth, and 

 colour. In normal snakes, however, the scales can be 

 treated of under three distinct heads : the shields on the 

 belly, the scales on the back and sides, and the shields of 

 the head. The ventral shields are of great importance, as 

 they are the organs of locomotion in snakes, taking the place 

 of limbs in other animals. A reference to the explanatory 

 part of the following table will show in how small a space, 

 and with what clearness, a full description of these shields 

 can be given for all Ceylon species. 



In the rat-snake (No. 24) the sub-caudals are two-rowed, 

 in the poisonous Bungarus (Nos. 43 and 44) simple. This 

 is a distinction that at once strikes the eye ; but striking and 

 important as this character generally is, the great snake-eating 

 snake of India {Ophiophagus) has them sometimes partly 

 two-rowed and partly simple. Another character that does 

 not immediately strike the observer, but which is very easily 

 seized and very important, is the character of the last ventral 

 or anal shield, whether it is simple or bifid. 



The ventrals may also be either smooth or keeled, and 

 when the keels are strongly developed we have another well- 

 marked type. 



These important characters give for Ceylon snakes five 

 * See Gtmther's " Reptiles of British India," p. 262, pi. XXII., fig. C. 



