IfiUi] Daniel: The Anatonui of 1I<_ ptaiicli Kg inacHlahis 351 



In the mid-dorsal line and at the posterior part of the eranium 

 is the occipital crest (o. cr.) which extends upward from the foramen 

 magnum (f.m.) to the parietal fossa (p.f.). At the bottom of this 

 fossa, as was described for Heterodontiis francisci (Daniel, 1915), are 

 the small openings for the endolymphatic ducts (e.d.), and nearer 

 the middle line the much larger foramina or fenestrae (/'«.). Behind 

 the parietal fossa, the posterior oblique semicircular canals radiate 

 outward and backward to the angles of the skull. Forward from the 

 fossa the roof is slightly convex and leads to the large anterior fon- 

 tanelle (F.) 



To the side of the anterior fontanelle there is a small perforation 

 if.o.p.') for the ophthalmic division of the fifth nerve, and back of 

 this a large opening (f.o. VII') fur the superficial division of the 

 seventh nerve. Continuing on a line posteriorly from this there is a 

 row of small foramina which mark the boundary of the supraorbital 

 crest. Through the,se, branches of the .superficial ophthalmic nerve 

 pass to the supraorbital canal. 



In side view (pi. 28. figs. 2 and 3) the cartilaginous rostral .supports 

 for the nose project slightly forward; at the base and sides of these 

 are the prominent olfactory capsules (oLc.) for the nasal apparatus. 

 The cartilages for the capsules are exceedingly thin-walled and open 

 to the exterior by the nasal apertures. Surrounding the aperture is 

 the arch-like nasal cartilage (n.c.) which in Hcptanclms is like the 

 letter A, the cross-bar of which is formed by a posterior and an 

 anterior projection. These projections sei-ve to divide the aperture 

 into a smaller upper and a larger lower opening. 



At the posterior third of the cranium is the auditory capsule 

 {a.c, fig. 2). in which the semicircular canals and the organs of 

 hearing are located. In dorsal view these capsules are strongly marked 

 by the anterior and posterior oblique (p.o.s., fig. 1) semicircular 

 canals; while laterally (fig. 2) each capsule is convex and but slightly 

 affected by the attachment of the hyoid arch. In side view, further- 

 more, the foramina for the ninth (/. IX) and tenth cranial nerves are 

 in close relation to the capsules. 



Between the auditory and the nasal capsule is the large orbit for 

 the eye. Overhanging this is the supraorbital crest (s.o., fig. 3), the 

 pre- ipr.o.) and the postorbital (po.o.) processes from which are well 

 developed. The preorbital process extends far ventralward and the 

 postorbital serves as an important attachment for the first visceral 

 arch. Ventral to the posterior part of the orbit the cranium bends 



