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TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



The cranial anatomy of the mail-cheeked fishes is the subject of a classic monograph 

 by Allis (1909), containing accurate descriptions of the cranial elements, the muscles, nerves 

 and blood-vessels, with many superbly executed illustrations of the skulls of representatives 

 of the principal families. I have also studied the dried skulls of most of the genera men- 

 tioned below. 



Scorpanids. — Among the least specialized of the living genera are Sebastes and Sebas- 

 todes, with numerous species. In general appearance these fish are distinctly bass-like, 

 except that the eye dominates the head and that the posterior border of the preopercular is 

 armed with five conspicuous points. In a dried skull of Sebastes marinus these points 



Sebastes marinus 



Fig. 200. Sebastes marinus. After Bigelow and Welsh. 



alternate with the large openings of the preopercular branch of the lateral line canal. The 

 projections on the preopercular margin are conspicuous in many scorpaenoids but subject 

 to wide modification in detail. Apparently they were characteristic of the stem scorpaenid 

 and may have originated in a pre-scorpaenid or bass-like stage, since more than a beginning 

 of this character is attained by the serranid genus bates. 



The skull of Scorpana also shows two prominent spikes on the posterior border of 

 the opercular (Fig. 201), projecting back over the opercular aperture. Both spikes are 

 large enough to inflict a wound by vigorous side strokes of the head and possibly the pre- 

 opercular spikes may serve the same purpose. There are also several pairs of small sharp 

 spikes on the top of the skull and on the posterior borders of the posttemporal and supra- 

 cleithral plates. In Scorpcsna scrofa (Fig. 203) and various other species of this family the 

 whole head bristles with sharp spikes. 



The two spikes on the opercular plate of our specimen of Sebastes (Fig. 202) have left a 

 clear record of their growth in the form of delicate wavy parallel lines like tide-marks or 

 folds. Evidently the two spikes were, so to speak, the growing tips of the outer border; 

 as they grew backward they also left another trail in the form of supporting ridges on the 

 scale-like plate. But why do these growing points have dense, sharply pointed tips like 



