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II. Sebasfes dactylopterus. 



The skull of Sebastes dactylopterus is relatively taller and shorter than that of Scorpaena 

 scrofa ; the orbits being relatively larger, the interorbital region narrower, the antorbital region shorter, 

 and the mid-dorsal line considerably more convex than in the latter fish. The space between the eyes 

 is concave. 



The ventral surface of the skull, starting immediately posterior to the dentigerous ridge on the 

 ventral surface of the anterior end of the vomer, is slightly convex, the summit of the convexity 

 lying beneath the foot of the basisphenoid. 



The internasal ridge is similar to that in Scorpaena, but the mesethmoid processes are smaller 

 and project almost directly forward instead of forward and upward. The bases of these processes 

 are connected by a curved transverse ridge, concave anteriorly, against the anterior surface of which 

 the hind end of the internasal ridge abuts and ends. Against the wide and slightly concave lateral 

 surface of each process the corresponding nasal rests, that bone being firmly bound to the process and 

 bearing, on the dorsal surface of its hind end, the nasal spine. 



Immediately lateral to the base of the mesethmoid process, there is a large aperture which 

 lies between the ectethmoid below and the anterior end of the frontal above. This aperture is the 

 anterior opening of that section of the supraorbital latero-sensory canal that lies in the frontal, com- 

 bined with the anterior opening of a small canal, between the ectethmoid and the frontal, that 

 transmits the rami ophthalmicus lateralis and ophthalmicus trigemini. Starting from this aperture, 

 a large rounded ridge runs backward between the orbits, curving at first shghtly toward the middle 

 line and then diverging slightly from it, and marking the course of the supraorbital latero-sensory 

 canal. Beginning slightly posterior to its anterior end, the ridge bears on its dorsal surface a narrow 

 ridge that runs posteriorly, concentric with the dorsal edge of the orbit, and, gradually increasing in 

 height, terminates in a spine. This spine lies posterior to the transverse commissure formed by the 

 fusion, in the middle line, of the fourth primary tubes of the supraorbital canals of opposite sides, 

 and overhangs the seventh or terminal tube of the supraorbital canal. It is accordingly the frontal 

 spine of the fish, and the narrow ridge that terminates in it is the frontal spinous ridge. The third 

 primary tube of the supraorbital canal opens on the dorsal surface of the frontal, lateral to this frontal 

 ridge, at about the middle point of the orbit. 



The hind border of the supraorbital commissure is marked by a slight ledge, that part of the 

 dorsal surface of the skull that lies posterior to the ledge lying at a slightly deeper level than the 

 part that lies anterior to it. The frontal spinous ridge, curving postero-laterally, crosses the lateral 

 end of the transverse ledge, and at this point, or from the mesial surface of the frontal ridge slightly 

 posterior to it, the parietal spinous ridge begins. Running backward and slightly laterally from there, 

 the parietal ridge terminates in the parietal spine, that spine lying directly above the supratemporal 

 cross-commissural canal. The anterior end of the parietal ridge lies on the hind edge of the frontal, 

 the remaining and larger part of it lying on the parieto-extrascapular. Immediately posterior to the 

 parietal spine, a short ridge begins on the dorsal surface of the extrascapular part of the parieto-extra- 

 scapular, and, continuing the line of the parietal ridge, terminates, at the hind end of the skull, in the 

 nuchal spine. 



The nasal, frontal, parietal and nuchal spines of Sebastes thus form a row of spines on the dorsal 

 surface of the skull that is strictly comparable to the middle row of spines in Scorpaena, but, as will 



