264 



VERTEBI; ATE AN IMALS. 



OltDEIt II. OPIIIDIA. 



This order includes iiio.st of the iiuiinids which would commonly 

 be called snakes or serpents, and is cliaracterised hy the following 

 peculiarities : The body is always more or less elongateil, wonu-like, 

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

 plates. There is never any bre;ist-l lone {xternum), nor pectoral arch, 

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

 In a few crises, however, rudimentary hinil-lindis can be detected. 

 The ribs are always very numerous. The two halves of the lower 

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



FIl:. isii.— Tlir ,V",/" '"',;■'', a poisonous Snake of Egypt- 



another in front (inly by liL,'a]iients and nuiscles (fig. I8ri). Hooked, 

 Clinical teeth are .-iKvays iiresent, liut they are never lodged in dis- 

 id are only u.sed to hold the prey, and not in 

 1 iitlicr ]i.-iired organs are often not 

 lirio" iisuallv smaller than the other. 



]'• 



tnict .sockets, 

 masticatiiiii. The hin; 

 synnnetrical, oiie iif e.ie 

 or altogethei- absent. 



The most .striking of these characters of the sn.-ikes (fig. 189) is to 

 be fiiinid in (he ii.iture of the organs of locomotion. The fore-limbs 

 are invioi.ilil \- altngether wanting, and there is no ])ectoral arch nor 



