70 ON THE PHYSIOGNOMY OF SERPENTS. 



ner different from its usual modes, and presents the colours of 

 the Ophidians under a light much less agreeable than just 

 after the casting of the skin. 



It results from the principles just laid doTvn, that the 

 form of the scales ought to depend on the direction of the 

 movements executed by the organs they protect. The 

 scales of the trunk are consequently disposed in lines paral- 

 lel to the contour of the ribs : the lines are intersected 

 by other lines at different angles, and thus the edges of the 

 scales are formed. The gi-eater or less regularity in the 

 form of the scales depends on the respective direction of 

 those lines : if those lines cross each other at right angles, 

 the scales will be of a square form ; if, on the contrary, 

 one of those lines be more inclined than the other to the 

 axis of the trunk, the scales will be rhomboidal, and will 

 approach to the lanceolate, or even the linear form, accord- 

 ing as these lines are less or more divergent from each 

 other. It happens almost always that these lines deviate 

 from their original direction in curving themselves to join 

 the middle range of plates below the animal ; hence the 

 form of the scales becomes more irregular as they recede 

 from the back, although they increase in size. It is uni- 

 formly on the anterior part of the trunk that these lines, 

 particularly those passing backwards, are inclined to the 

 jixis of the bodv : hence the form of the scales, which 

 cover that part of the body, should be assumed as the type 

 in descriptions. Towards the tail, and on that member, 

 the lines cross at almost a right angle, and these scales 

 consequently become less irregular. The different form of 

 the scales, on the different parts of the same individual, is 

 very apparent on the Naja and the Xenodon, where the 

 ribs of the neck, less arched than the others, and suscep- 

 tible of a considerable movement from behind to the front, 

 produce an enlargement of the volume of the body later- 

 ally. In the state of repose, the scales of this part cover 

 each other by their lateral edges ; they are in form nar- 

 now or linear, while those of the tail, imbricated in the 

 usual manner, are of a square form. 



The number of longitudinal ranges in which the scales 

 are disposed, vary not only according to the species ; these 



