THE SKULL. 



587 



palato-pterygoid attachment (pa.pg) of the quadrate subocular 

 bar becomes gradually elongated ; and, as it is so, the front end 

 of the subocular bar (sit) rotates outwards and backwards, and 

 soon forms a very considerable angle with the trabeculae. The 

 Meckelian cartilage (ink) at its free end becomes at the same 

 time considerably elongated. These processes of growth con- 

 tinue till (fig. 330) the palato-pterygoid bar (Pt) forms a sub- 

 ocular bar, and is considerably longer than the original sub- 

 ocular region of the quadrate ; while the Meckelian cartilage 

 (Mck) has assumed its permanent position on the hinder border 

 of the no longer suctorial mouth, and has grown forwards so as 

 nearly to meet its fellow in the median line. 



The metapterygoid region of the quadrate gives rise to a 

 posterior and dorsal process (fig. 339, ot.pr), the end of which is 

 constricted off as the tympanic annulus (fig. 340, a.t) ; while 



a.t- 



SO. b.o 



FIG. 340. YOUNG FROG, NEAR END OK FIRST SUMMER ; UPI'ER VIEW OF 

 SKULL, WITH LEFT MANDIBLE REMOVED, AND THE RIGHT EXTENDED OUT- 

 WARDS. (From Parker.) 



b.o. basioccipital tract; s.o. supraoccipital tract; Jo. frontal fontanelle; c.n. 

 external nostril; internal to it, internasal plate; a.t. tympanic annulus. 



Bones: <'<> exoccipital; pr.o. prootic, partly overlapped by /. parietal; f. frontal ; 

 cth. rudiment of sphenethmoid ; na. nasal ; pmx. premaxillary; nix. maxillary;/^, 

 pterygoid, partly ensheathing the reduced cartilage; q.j. quadratojugal ; sq. squa- 

 mosal ; ar. articular; d. dentary; m.nik. mento-Meckelian. 



the proximal part of the process remains as the otic (metaptery- 

 goid) process, articulating with the auditory cartilage. 



The pedicle (pd) retains its original attachment to the skull. 



