22 



THE BONES AND JOINTS. 



direction of their floors. The outer circumference of the head 

 forms a parabolic frame (Figs. 10 and n), composed of the 

 maxillary (;;/), premaxillary (2), and quadratojugal bones (j). In the 

 middle of this curved framework lies the elongated prismatic 

 cranium. Anteriorly, this is attached to the fore-part of the frame 

 by means of the cartilaginous skeleton of the organs of smell 

 (Fig. lie'); posteriorly, it widens out into two transverse arms (p), 

 which contain the organs of hearing. From this base, on either 

 side, a bony strut, composed of the posterior arms of the squamosal 

 (') and of the pterygoid bones, passes backwards to the hinder end 



Fig. ii. 



Skull of Rana esculenta, seen from above, 

 twice natural size. 



e Sphenethmoid. 

 */ Nasal.. x 



/.p. Fronto-parietal. 

 l_ i Premaxillary. 

 +j Quadrato-jugal. 

 <L> JIaxillary. 

 o Exoccipital. 



op Opisthotic. 

 i. p Prootic. 

 * pt Pterygoid. 

 pi' Posterior limb of pterygoid. 



* SquamosaL 

 t V Posterior arm of the same. 



Skull of liana csculcntu, seen from below, 



twice natural size. 



c Cartilaginous wall of skull. 



e Sphenethmoid. 



e' Cartilaginous skeleton of nu.->e. 



h' Stylo-hyoid. 



i PremaxiDary. 



m Maxillary. 



in' Quadrate tract. . 



o ExoccipitaL 



p Prootic. 



p' Anterior arm of prootic (ala ma<ja autt). 



l>" Trigeminal foramen. 



lil Palatine. 



pi Pterygoid.' 



pt' Postri-icir arm of pterygoid. 



* Para.sphenoid. 



v Vomer. 



of the frame. The anterior arm of the squamosal bone (t) does 

 not quite reach the framework, but is attached to it by ligament 

 alone. Between the last-named arm posteriorly, the cranium on the 

 inner side, and the maxillary frame-work laterally, is a large space 

 representing the orbital and temporal fossae of human anatomy. 



