SKELETON OF THE CROCODILE. THE SKULL. 257 



supratemporal arcade formed by the squamosal and post- 

 frontal. The postf rontal meets the parietal in front and forms 

 the anterior boundary of the supratemporal fossa. 



2. The Lateral temporal or infratemporal fossae. 

 These lie below and to the outer side of the supratemporal 

 fossae. Each is bounded dorso-internally by the supratemporal 

 arcade ; and behind by a continuation of the post-temporal bar 

 formed by the quadrate and quadratojugal. The external 

 boundary is the infratemporal arcade formed of the quad- 

 ratojugal and jugal, while in front the fossa is separated from 

 the orbit by the postorbital bar formed by the junction of 

 outgrowths from the postf rontal and jugal. 



3. The Orbits. Each is bounded behind by the post- 

 orbital bar, externally by the jugal forming a continuation of 

 the infratemporal arcade, in front by the lachrymal, and inter- 

 nally by the frontal and prefrontal. 



4. The Anterior nares. These form an unpaired open- 

 ing bounded by the prem axillae. 



Posterior surface. 



5. The Foramen magnum. The exoccipitals form the 

 chief part of its boundary, but part of the ventral boundary 

 is formed by the basi-occipital. 



6. The Pterygoid fossae. These form a pair of large 

 cavities at the sides of the occipital region of the skull. The 

 dorsal boundary is formed by the quadrate and quadratojugal, 

 the ventral by the pterygoid, the internal chiefly by the quad- 

 rate, pterygoid, alisphenoid, and basisphenoid. The trarispala- 

 tine forms a small part of the external boundary which is in- 

 complete. 



Ventral surface. 



7. The Posterior nares. These form a median unpaired 

 opening (fig. 43, A, 5) bounded by the pterygoids. 



8. The Posterior palatine vacuities. Each is 

 bounded by the maxilla in front, the maxilla and transpalatine 



R. 17 



