2 SNAKES OF CEYLON. 



their breadth noted, the shield before the anus (anal) examined 

 to see if it is entire or divided, and the shields beneath the 

 tail (subcaudals) examined to see if they are entire or divided 

 and then counted. It is best to begin at the tip and count 

 to the anus, so that the smallest shields are dealt with while 

 the eye is fresh to the work, instead of when strained and 

 tired. The necessity of the lens to the observer will at once 

 become apparent. All these things noted, attention should 

 then pass to the scales over the back (the costals or simply 

 " scales "). These should be counted from one side of the 

 ventrals to the other in three situations, viz., two heads- 

 lengths behind the head, midbody, and two heads-lengths 

 before the vent ; their relative breadth and length noted ; 

 and whether the vertebral or median row is enlarged or not ; 

 and any other details. After this the head shields should be 

 studied, each in detail, and noted. These and other details 

 will readily be grasped by reference to the various figures 

 which follow, the scales and shields in which are all lettered. 



It is advisable first of all to place your specimen in the 

 family to which it belongs, and this can be done by studying 

 the keys below. 



It must be borne in mind that the keys are based on the 

 characters of normal specimens. Many individuals, however, 

 show some aberration or other. This fact, the variation of 

 individuals, indeed is one of the essential bases upon which 

 the Darwinian doctrine of evolution rests. 



KEY TO FAMILIES. 



For Indian Species. 

 TAIL ROUND IN SECTION. Families. 



(A) Ventrals not enlarged (see fig. 3). 

 Anal divided into 3 or 4 (see fig. 3). 

 Costals broader than long (see fig. 3). 

 Eye beneath shields. Pupil round (see 

 fig- 2). 



(a) Costals in 16 to 36 rows at midbody Typhlopidae 



(b) Costals in 14 rows at midbody . . * Glauconiidse 



* Not represented in Ceylon. 



