722 B. W. KUNKEL 



portion of the hyomandibular branch continues in a posterior 

 direction in the space betweeil the quadratum and the otic capsule. 

 At the point at which the palatine branch reaches the sulcus 

 palatinus there is given off in a posterior direction the ramus com- 

 municans n. facialis cum n, glossopharyngeo which extends pos- 

 tero-laterally along the ventral surface of the chondrocranium 

 beneath the pars cochlearis of the otic capsule, the crista sub- 

 stapedialis, and the planum basale to unite finally with the ante- 

 rior end of the ganglion glossopharyngei. 



REGIO ORBITO-TEMPORALIS 



The orbito-temporal region shows the same general configura- 

 tion as that of Lacerta except that it is of much heavier and more 

 compact structure, being made up of broader plates instead of 

 slender rods. The fenestrae are also less numerous and relatively 

 smaller than in Lacerta, in which respect the chelonian skull 

 resembles more closely the primitive condition of Sphenodon. 

 The whole region has the form of a shallow longitudinal trough, 

 within which the anterior end of the brain is supported on its 

 ventral side. Ventral to the trough, the septum interorbitale 

 (s.i., fig. 9/ lies in a sagittal plane and increases in height from the 

 posterior to the anterior end. The sides of the trough are formed 

 by the pila prootica, the subiculum infundibuli, the pila metop- 

 tica, and the planum supraseptale. These walls are perforated 

 by the fenestrae prootica, metoptica, optica, and foramen oph- 

 thalmicum, besides a small perforation in the subiculum infun- 

 dibuli, present only on the right side of the embryo modelled 

 which represents the beginning of the absorption of the cartilage 

 at this point. 



As in all the Sauropsida, the orbito-temporal region is differen- 

 tiated into a posterior temporal and an anterior orbital portion. 

 The temporal portion is continuous behind with the otic region 

 and exhibits a basal and two lateral parts. The orbital region 

 is characterized by the high septum interorbitale which forms 

 a continuous wall between the two orbits. This septum is a 

 thin vertical plate, as will be described later; in the stage modelled 

 it is thin, but in younger embryos it is relatively thicker and made 



