ORDER OPtllDIA. . 249 



Its posterior extremity is enveloped in an oval and 

 corneous buckler.* 



The other tribe, or that of the Serpents, pro- 

 perly so called, has the tympanic bone, or pedicle 

 of the lower jaw, mobile, and almost always, sus- 

 pended to another bone, analogous to the mastoidian, 

 attached on the cranium by muscles and ligaments 

 which permit its mobility. The branches, likewise, 

 of this jaw, are united to each other, and those of 

 the upper jaw, to the intermaxillary only by liga- 

 ments, so that they can be separated more or less, 

 which gives to these animals the faculty of dilating 

 their throat so as to be enabled to swallow bodies 

 larger than themselves. 



Their palatine arches participate in this mobility, 

 and are armed with sharp teeth curved backwards, 

 the most marked and constant character of this tribe. 

 Their trachea is very long. The heart is placed 

 very far back. The majority have but one large 

 lung, with a small vestige of a second. 



These serpents are divided into venomous and 

 non-venomous, and the latter subdivided into 

 venomous with many maxillary teeth, and venomous 

 with isolated fangs. 



In the non-venomous, the branches of the upper 

 jaw are furnished all along, as well as those of the 

 lower jaw, and the palatine branches with teeth 



• Typhlops Philippinus, Nob. From the Philippine Islands ; eight inches 

 long, and entirely black. Ti/pklnps Oxyrhyncus, Schn. must approximate 

 very closely to it. 



