THE SKULL OF ACANTHIAS VULGARIS 425 



the origin of the first of the medial system of interarcuales 

 (Marion) — the subspinalia of Vetter's description (Int.arc.L). 



Except for the triangular rostrum (r), a lateral view of the 

 cranium (figs. 3 and 5) presents a very boxlike appearance, of 

 quite uniform depth and rectangular in general outline, the 

 posterior part being occupied by the otic capsule, the middle by 

 the orbit, and in front of the rostrum. 



The median rostral carina (r.c.) extends postero-ventrally 

 from the tip of the rostrum to a point medial to the nasal cap- 

 sule. The rostral bar (r.b.) is clearly shown connecting with 

 the carina and its dorsal and ventral connective tissue rami are 

 more distinctly seen in this view than in any other. The some- 

 what latero-ventral external naris is also visible. A lateral view 

 of the nasal capsule shows the dorso-lateral thickening of the 

 cartilage mentioned in connection with the ventral view. It 

 may be considered a forward extension from the strong ant- 

 orbital process {p. a.). 



The orbit, in a lateral view, is a large concavity occupying the 

 dorso-ventral extent of the cranium. As mentioned above it 

 is roofed by the supraorbital crest (s.or.c.) which passes in front 

 into the ant- and behind to the post-orbital process; these form- 

 ing, respectively, the anterior and posterior boundaries of the 

 orbit. Along the ventral margin of the orbit are seen, posteri- 

 orly, the basal angle (b.a.) and just anterior to it, on the narrow 

 interorbital region, the depression of the palato-basal articular 

 surface (p. b.a.). 



The floor of the cranium slopes upwards from the basal angle 

 to a region just behind the level of the postorbital process and 

 then extends horizontally, so that the depth of the cranium in 

 the otic region is less than in the orbit. A horizontal ridge 

 through about the middle of the otic capsule marks the position 

 of the horizontal semicircular canal of the ear (h.c). Posteri- 

 orly this ridge extends toward the fenestra postotica (f.po.). 

 Behind the fenestra the triangular occipital condyle is visible 

 (ox.). The middle part of the braincase appears above the 

 level of the supraotic and supraorbital crests. At the base of 



JOURNAL OF MORPHOLOGY, VOL. 28, NO. 2 



