THE EPIMERE (SEGMENTAL OR VERTEBRAL PLATE) 



Orbito-nosal foramen 



Auditory 

 capsule- 



215 



cartilage 



Paloto-quadrate 

 cartilage 



Posterior maxillary 

 process 



Polato-quadrate 

 (anterior ascend- 

 ing process) 



Anterior maxillary 

 process 



Palato-quadrate 

 (pterygoid process) 



Olfactory cartiloge 



Anterior 



maxillary process L'l 



Pre-maxillary bone 



Nasal bone 

 Maxillary bone 



Pterygoid bone 



Palato-quadrate 

 (ascending pro 

 cess) 



Palato-quodrqte, 

 {pterygoid ~' ' 

 process) 



Proof ic 

 foramen 



Annulus .-|^ 



tympanicus 



Palato-quadrate 

 cartilage (orticu 

 process) 



Auditory capsule 



Skull of Rana during metamorphosis. (A) Chondrocranium of R. fusca 

 during metamorphosis, lateral view. (B) Skull of R. fusca after metamorphosis, 

 dorsal view. The membrane bones are shown removed from the left side. (After 

 Gaup, from Ziegler.) 



Plectrunn 



Quadrato- 



jugular 



bone 



united with the parachordals on either side. The cartilaginous ele- 

 ments of the skull appear by the time of hatching and form what is 

 known as the chondrocranium. These elements are not displaced by 

 bone until about the 30 mm. body length stage. 



Anterior to the parachordal plate, and continuous with it, is an- 



