THE SKULL. 



73 



one iu certain points of that of Petroinyzon, 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 



Itbrl 



KIT 



-KeLC 



FIG. 60. HYUBRANCHIAL APPARATUS OF UKODELES. A, Axolotl (Siredon jrisci- 

 formis) ; B, Salamandra maculata ; C, Triton cristatus ; D, Spelerpcs fuscus. 



libr I, II, first and second basibranehial ; KcH, ceratohyal ; ffpJf, hypohyal ; 

 Kebr I, II, first and second ceratchranchial ; Epbr I to IV, first to fourth cpi- 

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

 bone; G.th, thyroid gland. 



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 



