Obdo II. OPHIDIA. 



The Serpents or ophidian reptiles constitute the most characteristic 

 order of the CLass. Their body is elongated, generally rounded, 

 narrow, and, in most cases, diminishing towards both extremities. 

 There are neither limbs nor fins disposed in pairs on the sides of the 

 body, as in most lizards, salamanders, all the toads and frogs, and 

 tortoises. There are, however, a few instances in which rudiments 

 of posterior limbs make their appearance outwardly, under the shape 

 of horny knobs or hooks. The jaws are endowed with the property 

 of being highly dilatable, and thus permit a large prey to enter the 

 buccal cavity. Acerated or hook-like teeth exist upon the jaws gene- 

 rally, and also upon the palatine and pterygoid bones. The eyes are 

 either rudimentary or else well developed ; in no case is there a 

 movable eyelid. The organ of audition is not made apparent out- 

 wardly ; there being neither an aperture nor a tympanic membrane. 

 Their skin is rather tough, capable of great extension, beset with 

 scales or granules, and covered by a continuous epidermis, which is 

 cast and reproduced several times during the year. 



Such are the most striking characters of the order of reptiles we 

 are now treating of. More detailed information may be found in the 

 "Erpetologie g^nerale." 



The w^ant of a more complete series of ophidians, either in this or 

 other collections available for our investigations, has rendered the ar- 

 rangement of the following ones into families, one of the most difficult 

 point. The classification recently proposed by Dumeril, we could not 

 adopt a priori, and lacking the proper materials to satisfy ourselves 

 as to the value of the families by him established, we renounced alto- 

 gether heading these groups, placing the genera one after the other, 

 according to their apparent zoological affinities. 



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