264 



VERTEBRATE ANIMALS. 



Order II. OriiiDiA. 



This order includes most of the animals which would commonly 

 be calleil snakes or seipents, and is characterised by the following 

 peculiarities : The body is always more or less elongated, wi:irm-like, 

 or cylindrical, and the skin develops horny scales, but never bony 

 plates. There is never any bi'east-bone (stenmin), nor pectoral arch, 

 nor fore-limbs ; nor, as a rule, are there any traces of hind-limbs. 

 In a few cases, however, rudimentary hind-limbs can be detected. 

 The ril is are always very numerous. The two halves of the lower 

 jaw are composed of several pieces each, and they are united to one 



Fi;^'. ISO.— Tlic NdJ" h"j'-, a V^iisouous Snalce of K.nypt. 



another in front only by ligaments and muscles (fig. 185). Hooked, 

 conical teeth are always present, biit they are never lodged in dis- 

 tinct sockets, and are only used to hold the prey, and not in 

 mastication. The lungs and other ]iaiied organs are often not 

 synmietrical, one of each pair being usually smaller than the other, 

 or altogether aljsent. 



The most stiiking of these characters of the snakes (fig. 189) is to 

 be found in the nature of the organs of locomotion. The fore-limbs 

 are invariably altogether wanting, and there is no jiectoral arch nor 



