72 



COMPARATIVE ANATOMY. 



becomes fused with the corresponding palatine (Fig. 58, Vop) 

 which forms a delicate bar lying on the ventral surface of the 

 parasphenoid. These relations are secondary, for in the larval 

 condition a typical palatoquadrate or pterygo-palatirie bar is present 

 (Fig. 56, Pt, Pic, PI). 



On the outer side of the vomer lies the maxilla (Figs. 56 to 58, 

 M], and in front of this a premaxilla (Pmx) which usually encloses, 

 or at least bounds a cavity. The latter bone extends on to the 

 dorsal surface of the skull, and abuts against the nasal, behind 

 which usually follows a prefrontal (Fig. 57, N, Pf). 



The suspensorium is much more simple than that of Fishes, 

 as a glance at the diagrammatic Fig. 48, E, will show. It con- 

 sists of the quadrate only, which secondarily becomes fused with 

 the skull, and on the outer surface of which an investing bone, the 

 squamosal, becomes developed (Figs. 56 to 58, Squ). 



The skull of the Gymnophiona, which is characterised by its extreme, 

 strength and solidity, reminds us of that of the fossil genera of Amphibia of 

 the Carboniferous period. It shows in many points a certain relationship to 

 the skull of Anura, and is of great interest on account of the very complicated 

 structure of the nasal capsule (compare the chapter on the olfactory organ). 



PP 



f/Ofc 



Flu. 59. SKULL OF Sana csculenta. (Ventral view.; (After Ecker.) 



The investing bones are removed on the right siilc. 



Cocc, occipital condyles ; Olat, exoecipital ; GK, auditory capsule ; Qu, quadrate ; 

 Qjg, quadratojugal ; Pro, prootic ; Ps, parasphenoid ; As, alisphenoid region ; 

 Pt, bony pterygoid ; PP, palatopterygoid ; FP, frontoparietal ; E, sphonethmoid 

 (girdle-bone) ; Pal, palatine ; Vo, vomer ; M, maxilla ; Pmx, premaxilla ; 

 N, JV 1 , cartilaginous supports of the nose ; //, V, VI, foramina for optic, tri- 

 geminal, and abducent nerves. 



Anura. The skull of the tailless Batrachia is at first sight very 

 similar to that of Urodeles. It undergoes, however, an essentially 

 different and much more complicated development, reminding 



