SKULL 



105 



especially in the parts surrounding the gape, an essentially 

 different and much more complicated development, and cannot in 

 any way be directly derived from that of tailed Amphibians, so 

 that the common ancestral form must be sought in very^early 

 geological periods. The chondrocranium (Figs. 77 and 78) is 

 much more extensive than in Urodeles, and is largely retained in 

 the adult, the bones not gaining the upper hand to such an 

 extent. 



The larva, or tadpole, in adaptation to the nature of its food 

 and mode of feeding, possesses a suctorial mouth, provided with 



c 



E.vt. H0*tril Oblique 

 \ ' 



Frontal font a nelt<- 



I 



Parietal fawtanette 



Alar curt. 



\Sup. i>,*> - 

 cart. 



Inf. j>,-' - 



cart. 



Tect. syn. 



Afaxillary i>r<.><-' ss 



I 

 Arc. f>ii hoc. 



FIG. 



c. 



Fenestra 

 n Palis 



tympanitis Artie, proccs&oj 

 quadrate 



LATERAL VIEW OF A WAX MODEL, RECONSTRUCTED FROM SECTIONS, OF THE 

 CHOXDROCRANIUM OF A YOUNG Eana temporaria, ABOUT 2 CM. LONG. The 

 Stapedial Plate and Columella are removed, and the Ossifications are not 

 indicated. (After Gaupp. ) 



labial cartilages and horny jaws and denticles. The articulation 

 of the lower jaw with the palatoquadrate is situated very for 

 forwards, and at metamorphosis becomes shifted backwards, 

 thus causing a considerable widening of the gape of the 

 mouth. 



An important advance on other Amphibia is seen amongst 

 Anura (e.g. Ranidae) in connection w r ith the auditory organ. The 

 first visceral (hyomandibular or spiracular) cleft disappears entirely 

 during development in the Urodela and Gymnophiona, but 

 becomes modified in many Anura to form a Emtacliian tube, 

 opening into the pharynx and leading into a tympanic cavity. 

 The latter is closed externally by a tympanic membrane supported 

 by a cartilaginous ring (annulus tyrnpanicus^ Figs. 77, (7, and 

 78), and to it the distal end of the columella (p. 98) is attached. 



1 Cf. under Auditory Organ. The tympanic ring is a derivative of the 



palatoquadrate. 



