REPTILES 



209 



prey with their poison and the constrictor snakes by crushing before 

 swallowing it; other snakes do not stop to kill the prey but swallow 

 it alive. Snakes live in a great variety of localities, some species 



Fig. 113. — A portion of the skin of Lampropellis getulus, showing 23 rows of scales {from 



Blanchard). 



-~^> 



being terrestrial, others arboreal; a large number are aquatic, some 

 living in the open sea. Many species are brightly colored, especially 

 in the tropics, but in none has metachrosis, so common among Kzards, 

 been observed. 



On the Identification of Snakes. — The length 

 in miUimeters of an average adult specimen from 

 the tip of the snout to the tip of the tail and also 

 the length of the tail alone, are first given, followed 

 by a description of its coloration. Those scales 

 which lack the keel are said to be smooth, and these 

 are usually much more glistening than keeled scales, 

 which are dull in appearance. In some snakes only 

 the dorsal scales are keeled, while those of the sides 

 arc smooth. The number of rows of scales (Fig. 

 113) is .always important in the description; the 

 number of ventrals is also often important; also 

 the number of subcaudals, and whether a single or 

 a double row is present. Whether the anal plate is 

 single or divided is a very important character 

 (Fig. 114). 



In most species both dorsal and ventral surfaces of the head are 

 covered with symmetrical plates, which are often important in descrip- 

 tions (Fig. 115). 



Fig. 114. — A portion 

 of the ventral surface 

 of A b a si o r erythrog- 

 rammiis: i, ventrals; 2, 

 anal plate (which is 

 here divided); 3, aniis; 

 4, subcaudals (from 

 Cope) . 



