THE SKULL. 



one in certain points of that of Petromyzon, and it cannot there- 

 fore be derived in any way directly from that of Urodeles. 



A suctorial mouth, provided with labial cartilages and horny 

 teeth, is present in the larva. Far more important, however, is the 



Tlttrl 



KIT 



JCeJl 



FIG. 60. HYOBEANCHIAL APPARATUS OF URODELES. A, Axolotl (Siredon pisci- 

 form-is); B, Salamandra maculata; C, Triton cristatus ; D, Spelerpcs fuscus. 



Bbr I, II, first and second basibranchial ; KcH, ceratolij-al ; JffpH, hypohyal ; 

 Xebr I, II, first and second ceratcbranchial ; Epbr /to IV, first to fourth cpi- 

 branchial ; KU, KH 1 , small anterior and posterior pairs of cornua ; O.th, thyroid 



bone ; G.th, thyroid^land. 



r 



formation of membranous and cartilaginous walls to the tympanic 

 cavity, which is closed externally by a tympanic membrane, 

 while internally it opens into the mouth by a Eustachian aperture. 

 The palatoquadrate bar unites anteriorly with the lateral part of 



