1 88 



THE SKULL. 



[CHAP. 



Behind this the exoccipital gives off a very long paroccipital 

 process (pp\ 



The periotic and tympanic are ankylosed together, but not 

 with the squamosal. The former has a wide but shallow 

 floccular fossa on its inner side, and sends backwards a 

 considerable " pars mastoidea " which appears on the outer 



surface of the skull (Per) between the 

 post-tympanic process of the squamosal 

 and the exoccipital. The tympanic (Ty) 

 forms a tubular meatus, directed out- 

 wards and slightly backwards. It is 

 not dilated into a distinct bulla, but 

 ends in front in a pointed styliform 

 process which forms part of the outer 

 wall of the Eustachian canal. It com- 

 pletely embraces the truncated cylin- 

 drical tympanohyal (t/i), which is of 

 great size, corresponding to the large 

 development of the whole anterior arch 

 of the hyoid. 



The stylohyal (Fig. 61, s/i) is of great 

 size, compressed, and expanded at the 

 upper end, where it sends off a tri- 

 angular posterior process. Below the 

 FIG. 61. Superior surface stylohyal, and usually becoming anky- 

 i jlstyiohyai;/fe cera- losed with it, is a small nodular bone 

 Shyrotyaf bas ' ihyal ' '* (epihyal), and then the arch is com- 

 pleted by a short cylindriform cera- 

 tohyal (f/i). The basihyal (bh) is rather flattened from 

 above downwards, arched with the concavity behind, and 

 sends forwards a long, median, pointed, compressed 

 " glossohyal " process. The thyrohyals (th) are compressed 

 bars projecting backwards from, and in adult animals 



