THE SKULL 



87 



Eustachian aperture. With the exception of certain small regions 

 (fenestrae) on the dorsal side, the skull of Anura forms a com- 



FIG. 68. RESTORATION OF THE SKULL OF A STEGOCEPHALAN (from the 

 Carboniferous of Bohemia). (After Fritsch.) 



Pmx, premaxilla ; J/, maxilla ; N, nasal ; Na, nostril ; F, frontal ; Pf, prefrontal ; 

 P, parietal ; Fp, parietal foramen ; Socc, supraoccipital ; Br, branchial 

 apparatus ; Oc, sclerotic ring (orbital bones. ) \ 



plete cartilaginous box, the ethmoid region being at first entirely 

 cartilaginous, and later becoming ossified by a sphenethmoid, which 



PP 



occ 



FIG. 69. SKULL OF Rana esculenta. Ventral view. (After Ecker. ) 

 The investing bones are removed on the right side. 



Coc.c, occipital condyles ; Olat, exoccipital ; GK, auditory capsule ; Qu, quadrate ; 

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

 Pt, bony pterygoid ; PP, palatopterygoid ; FP, frontoparietal ; E, spheneth- 

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

 A", A n , cartilages in connection with the nasal capsules; W.K, prorhinal 

 cartilage ; //, V, VI, foramina for optic, trigeminal, and abducent nerves. 



