THE SKULL OF ACANTHIAS VULGARIS 427 



In the anterior part of the floor of the otic region are two 

 foramina, separated by a rather prominent projection, through 

 which pass the hyomandibular branches of the facial nerve 

 (hym.) In the extreme posterior part of the otic region, just 

 above the fenestra pos^otica is the notch in the cranium in 

 which is the glossopharyngeal foramen (IX). 



Besides the points of origin of the eye muscles, there are two 

 important regions of muscular attachment on the lateral sur- 

 face of the cranium. One of these, just behind the postorbital 

 process and below the supraotic crest, is the origin of the levator 

 maxillae superioris (l.m.s.). Posterior to this and just below 

 the postotic process is the origin of the second constrictor 

 superior dorsalis (csd.2). 



The basal surface of the cranium presents little not already 

 described (fig. 7). Ventrally, in the middle line is the articular 

 surface for articulation with the centrum of the first vertebra, 

 and just lateral to it, on either side, is an occipital condyle {ox.). 

 Above these is the foramen magnum (f.m.), from which the crista 

 occipitalis extends to the posterior margin of the fossa endo- 

 lymphaticus (o.c). Laterally is the elevation over the pos- 

 terior semicircular canal of the ear (p.c). Near the postero- 

 lateral angle the fenestra postotica (fpo.), and the foramina for 

 the ninth (IX) and tenth nerves (X) are visible. 



Figure 4 shows a median section and the inner surface of half 

 of the cranium. The roof is rather uniform in thickness, except 

 for a marked thickening just behind the endolymph fossa and 

 a lesser one behind the anterior fontanelle. The floor, however, 

 shows marked variations in this respect, being thicker below 

 the regions of pro- and mesencephalon than below the posterior 

 regions of the brain, The section of the rostral carina makes 

 that part appear thicker. The floor rises in the posterior part 

 of the cranium, and in this part the notochord (nch.) runs, 

 from the posterior end of the skull forward to the dorsum sellae, 

 turning doi sally to enter this projection. Just anterior to the 

 dorsum (d.s.) is a rather deep pit, the fossa hypophyseos (f.h.) 

 or sella turcica, in which the infundibulum, hypophysis and 

 associated structures lie. 



