CECILIA. 217 



anterior and external to the three larger teeth. For a double series of 

 teeth, thus occasioned, does not exist in the maxillary or preman- 

 dibular bones of any Batrachian or Saurian reptile ; and, in the mam- 

 malia, the only instance of such a disposition of the teeth is the 

 exceptional presence of the small incisors behind the dentes scalprarii 

 of the hares and rabbits ; but the location of large tusks in front or 

 behind a row of smaller teeth is a character which has hitherto been 

 met with only in the jaws of fishes. This, therefore, must be 

 regarded as another of the Ichthyic characters which are retained in 

 the lowest forms of reptiles, and which is thus manifested in a new 

 way in the primeval Batrachians, whose dental characters and pecu- 

 liarities we have been endeavouring to interpret. 



90. In the extinct family of the Labyrinthodonts the Batrachian 

 type of organization was modified so as to lead directly from that order 

 to the highest forms of reptiles, viz : the loricate or crocodilian Sauria ; 

 some of the existing edentulous genera of Bufonidce connect the 

 Batrachian with the Chelonian order ; the family founded upon the 

 Linnsean genus Ccecilia forms the transition to the Ophidian rep- 

 tiles. The characters which retain the Csecilise in the Batrachian 

 order are generally known, and may be briefly enumerated as the 

 double occipital condyle, the biconcave vertebrae, the smooth mucous 

 integument with minute and concealed scales, and the branchial aper- 

 tures retained by the young some time after their birth. In the fixed 

 tympanic pedicle and the anchylosed symphysis of the lower jaw the 

 Csecilise are also far removed from the typical ophidian structures ; but 

 the teeth in their length, slenderness, sharp points, wide intervals and 

 diminished number begin to exhibit the characters of the dental system 

 of the serpent tribe (PI. 65, figs. 1 &2). They are implanted in a single 

 row upon the maxillary, intermaxillary and palatine bones, the upper 

 jaw being thus provided with two semi-elliptical and sub-concentric 

 series ; there are also two rows of equal-sized teeth on the premandibu- 

 larbonesof the lower jaw, in certain species; and the Ccecilia is the last 

 example, in the ascending survey which we have taken of the dental 



