70 The Alligator and Its Allies 



internal carotid (15). Another large foramen in 

 the exoccipital bone will be seen and described in 

 connection with the posterior view of the skull. 

 Dorsal to the quadrate and largely bounded by it 

 is the wide external auditory meatus (16), which 

 leads into the tympanic cavity. This cavity is 

 complicated by a number of canals that lead from 

 it in various directions. Overhanging the cavity 

 and meatus is the squamosal bone, described in 

 connection with the dorsal aspect of the skull. 



The Posterior Aspect (Fig. 22). Most of the 

 bones seen in this view have already been described. 

 The pterygoids (10) form the two prominent, ventro- 

 lateral projections, while dorsal to these is the large 

 process formed by the quadrate (8) and quadrato- 

 jugal (12). The dorsal margin is formed by the 

 edges of the parietal (23) and the squamosals (7). 

 Immediately below the parietal is the supra- 

 occipital (26) ; it is a small, triangular bone, articu- 

 lating above with the parietal and squamosals, 

 below with the exoccipitals, and anteriorly with 

 the epiotic. It takes no part in the formation of 

 the foramen magnum. 



The exoccipitals (13) form the entire boundary of 

 the foramen magnum except the narrow ventral 

 portion formed by the basioccipital. Each exoccipi- 

 tal is a wing-shaped bone, articulating dorsally with 

 the squamosal and supraoccipital, ventrally with 

 the quadrate, basioccipital, and basisphenoid, and 

 anteriorly with the opisthotic. It is pierced by 



