— 6 — 



dorsal surface of the lateral edge of that bone ends in a spine that would seem to be the exoccipital 

 of Jordan & Evermann's descriptions. Posterior to this suprascapular spine, and in line with it, the 

 dorsal edge of the supraclavicular ends in a more or less pointed corner, but there is here no regulär 

 spine. Between the pterotic spine and the anterior end of the suprascapular spinous ridge, the lateral 

 edge, or the postero-lateral corner, only, of the lateral extrascapular intervenes; and on that corner 

 there is a small sharp prominence, rather than spine. This prominence forms the postero-lateral 

 end of a small ridge which extends, from there, antero-mesially across the dorsal surface of the bone. 



These several additional spines thus form a lateral row on the dorsal surface of the skull, one 

 or more of the spines being found on each of the dermal bones that form the lateral portion of the 

 dorsal surface of the skull, the lateral extrascapular excepted. But it is to be noted that the post- 

 frontal spines lie lateral to the anterior end of the pterotic spinous ridge, and that that ridge is 

 continued anteriorly by the slight ridge, already described, that leads toward the point from which 

 the frontal commissure arises from the supraorbital canal. 



Between the hind ends of the lateral and mesial rows of spines, there is a short row of two 

 small spines, one on the hind edge of the lateral extrascapular and the other on the hind edge of 

 the epiotic process of the suprascapular. 



Considering, now, the posterior portion only of the dorsal surface of the skull, there are seen 

 to be, on each side, four ridges or lines of ridges diverging approximately from the frontal spine. 

 One of these ridges is the commissural ridge, which extends postero-mesially to the mesial edge of 

 the frontal; and another is the postocular spinous ridge which extends almost directly laterally to 

 the lateral edge of the same bone. Between these two ridges are the parieto-nuchal and pterotic 

 ridges, both extending backward, but diverging. These four ridges thus divide the posterior portion 

 of the dorsal surface of the skull of Scorpaena into three regions which are seen to be strikingly similar 

 to the regions occupied by the supratemporal, temporal and dilatator grooves of Scomber (Allis, 

 '03) ; and the three grooves of Scomber would arise if the three regions in Scorpaena were to undergo 

 a depression, this depression being accompanied by a diminution in size and a backward translation of the 

 lateral extrascapular, and by a Separation of the postfrontal from the underlying bones of the skull. 



SUBQUADRANGULAR GROOVE. 



The subquadrangular groove on the vertex of Scorpaena is a single median depression, which 

 occupies the position of the two supratemporal grooves, united, of Scomber. Laterally it is bounded, 

 on either side, in part by the parietal spinous ridge, and in part by the ridge that runs backward 

 from the base of the frontal spine immediately lateral to the parietal spinous ridge, this second ridge 

 bearing no spine. The anterior edge of the groove is reentrant, and is formed, on either side, by the 

 corresponding commissural ridge. Posteriorly the groove is bounded by a transverse ridge on the 

 dorsal surface of the supraoccipital, this ridge being heightened by superimposed, transverse sutu- 

 rating processes of the parieto-extrascapulars. The parietal spine lies at the lateral end of this trans- 

 verse ridge, and hence at the postero-lateral corner of the groove. The frontal spine lies at the antero- 

 lateral corner of the groove. The floor of the groove is formed mainly by the frontal and parieto- 

 extrascapular bones, but a small median portion of the supraoccipital is exposed near the middle 

 point of the groove. These same three bones, on either side of the head, form the floor of the larger, 

 anterior portion of the supratemporal groove of Scomber, the extreme posterior portion of the floor 

 of the groove, in this latter fish, being formed by the supraoccipital and epiotic. The groove, in 



