190 



JOURNAL, R.A.S. (CEYLON). 



[Vol. XI. 



including the species from 35 to 41, in which one or more of 

 the last teeth in the upper jaw are grooved, Both series 

 include types of different appearance to the eye. We may 

 therefore look upon typej as an imitation of type a, but differ- 

 ing in a fundamental point of structure. The same order of 

 relation is of constant occurrence in the animal kingdom. 

 Thus, many marsupial mammals are externally, in some cases 

 exactly, like species belonging to orders very far removed 

 by their anatomical characters. All such cases of difference 

 of structure disguised by similarity of appearance should be 

 expressed by a letter. 



Habits and Geographical Distribution, 



These subjects have been so little worked out that the 

 student must consider the tables as mere sketches to show 

 that they are susceptible of the same treatment as the actual 

 material facts expressed in the animals themselves. The 

 anatomical characters can of course be tabulated in the same 

 manner ; but in order to do this a complete collection of 

 skeletons and specimens showing the myology, splanchnology, 

 and neurology of Ceylon snakes would be required. 



Colour. 



Colour, in the limited number of snakes found in Ceylon, 

 is scarcely susceptible of a natural classification. 1 think, 

 however, that in all cases — even if treating of the birds of 

 the world, for instance — that the plan adopted in the 

 following table would be an advantage. An artificial key is 

 given by arranging the species according to the colour of the 

 belly, which is either white or yellow, immaculate, or more 

 or less spotted with black, or of much the same tint as the 

 rest of the body, or, in a few cases, darker. Then the general 

 ground colour and the position of each tint is given, com- 

 mencing with the black and going through to the white in 

 the order of their intensity. This plan admits of great 

 condensation of the descriptions, and by observing the 

 black marks alone many species can be identified with 



