904 SUB-KINGDOM VERTEBRATA. 



squamoso-prefrontal) arcade formed by the squamosal, postorbital, 

 and postfrontal ; while the lower or infratemporal fossa is bounded 

 superiorly by the last-named arcade, and below by an inferior tem- 

 poral (or quadrato-maxillary) arcade, formed in most Reptiles (fig. 

 826) by the quadrate, quadratojugal, jugal, and maxilla. In the 

 Mammalia (where it is usually termed the zygomatic arch) we find, 

 however, a single arcade formed by the squamosal, jugal, and max- 

 illa, and a similar arcade, but with the apparent absence of the 

 jugal, occurs in many of the Anomodont Reptiles. This may be 

 termed the squamoso-maxillary arcade. In many Sauropsida, when 

 a postorbital or postfrontal is developed, these two arcades are 



Fig. 826. — Right lateral aspect of the cranium of Sphenodon punctatus. The lower vacuity 

 on the left is the infratemporal fossa, bounded below by the inferior, and above by the superior 

 temporal arcade ; the vacuity above the latter being the supratemporal fossa. The posterior 

 border of the latter fossa is formed by the parieto-squamosal bar. The quadrate is on the left 

 lower corner of the figure. (After Giinther.) 



usually connected behind the orbit by a process from the for- 

 mer articulating with another from the jugal, and thus forming a 

 bar or arch which may be termed the postorbital bar or arch. 

 Similarly another bar at the posterior extremity of the supratem- 

 poral fossa is formed by the quadratojugal (or quadrate), squa- 

 mosal (the supratemporal of fig. 824 being absent), and parietal, 

 and may be termed the posttemporal, or parieto-squamosal bar, or 

 arch. A third fossa behind this bar is termed the posttemporal 

 fossa. It will be observed that these numerous vacuities expose to 

 view the brain-case lying within these arches or bars ; and there 

 seems to have been a gradual tendency to open up the completely 

 roofed skull of the Labyrinthodont Amphibia till in the Mammals 

 we find, as already mentioned, the squamoso-maxillary, or zygomatic 

 arcade, and often a postorbital bar, as the sole remnants of this 

 primitive secondary roof. 



It will not be necessary to mention the various neural and vascular 

 foramina of the cranium, but it must be observed that on the upper 

 aspect there are paired apertures for the orbits (fig. 826), and either 

 paired or single ones for the nares (ibid.); while between these aper- 

 tures there may be the paired preorbital vacuities, which are shown 



