224 



THE FROG— THE PLATANA 



squamosals, exoccipitals and pro-otics. The quadrato-jugals are well developed ; 

 but the quadrate consists of a piece of cartilage at the posterior end of the 

 quadrato-jugal, between the pterygoid and the squamosal. The lower jaw 

 articulates with the quadrate cartilages. The columella is usually not well 

 shown. Between the various bones of the skull there are considerable areas of 

 unossified cartilage, persistent parts of the original chondrocranium. 



Naaal 



Supra ethmoid 



Septomaxillary 



-Maxilla 



'Spbenethmoid 



SquamosaN- 

 Fronto-parietal-- 

 Extrastai^edial 



Squamosal V '^\ 

 Quadra to-jusal 



Maxilla 



Occipital condyle i EScdccipital 

 Foramen magnum 



Columella 

 Pro-otic 



SU-praoccipital ; ^Occipital condyle 



Foramen magnum 



A B 



Fio. 80. — ^A. Dorsal View of the Skull of Saiia ; and B, of Xenopus 



[In the Platana the fronto-parietals, nasals, supra-ethmoid, preinaxillce, 

 maxilke, squamosals, exoccipitals, and pro-otics are well shown. The quadrata- 

 jugals are very inconspicuous. An extrastapedial plate of cartilage is well 

 developed, and the bony columella may be seen lying underneath it. . The sides of 

 the skull consist of bones which represent the orbitosphenoids and alisphenoids of 

 higher types. The supra-occipital is represented by a small cartilage.] 



Make a drawing of the dorsal aspect of the skull. 



Premaxilla 



"\ 



i Pterygoid 



-^ 



A B 



Fig. 81. — A. Ventral View of the Skull of Rana ; and B. of XenopuK. 



