418 GRACE A. WELLS 



The dorsal surface (fig. 1) is somewhat like the head of a 

 spear in outline, the point of the spear being the anterior end, 

 the so-called rostrum (r). The rostrum is flanked on either 

 side at its base by a nasal capsule (n.c.) } a rather deep rostro- 

 nasal notch (r.n.) intervening between rostrum and capsule. 

 Each nasal capsule is bounded by a shallow vertical groove, 

 limiting the capsule from a strong antorbital process (p. a.), the 

 lateral aspect of which will be described later, but which passes, 

 on the dorsal surface of the cranium, into the supraorbital crest 

 (s.or.c). The lateral margin of each supraorbital crest runs 

 obliquely inwards and backwards to the region between and a 

 little posterior to the eyes, and then bends sharpty outwards to 

 form the dorso-anterior margin of the strong postorbital process 

 (p.o.), which is triangular in outline as seen from above. The 

 sharp dorsal margin of the postorbital process continues back 

 as an acute supraotic crest (s.ot.c.) on the dorso-lateral surface 

 of the otic capsule, and then bends obliquely downwards and 

 backwards, terminating at the latero-posterior angle of the 

 skull, in the postotic process (p.ot.). 



The brain case (br.) lies in the median line between the supra- 

 orbital and supraotic crests, and is marked off from the lateral 

 sense capsules by a longitudinal depression — the sulcus longi- 

 tudinalis (s.l.) on either side. Each sulcus begins in front, at 

 the rostro-nasal notch, lateral and ventral to the superior mar- 

 gin of the rostrum, continuing back, as a broad groove, to behind 

 the nasal capsules, where it is narrow and shallow. At about 

 the line of the middle of the postorbital process it is interrupted, 

 but continues again as a groove on the dorso-lateral wall of the 

 otic capsule, finally terminating on the basilar aspect of the skull 

 at the foramina of the ninth nerve (IX). 



The rostrum is somewhat oval, in a dorsal view, and forms a 

 trough, open above, shallow in front and deeper behind. The 

 opening to the trough is the anterior fontanelle (a.f.). Like 

 other sharks the adull Acanthias has no posterior fontanelle. 

 The fontanelle is about two and one-half to three times as long 

 as broad. The anterior end of the rostrum has the cartilage 

 walls thickened. The lateral walls of the rostrum are thin, ver- 



