THE PERCH FAMILY. 103 



BLACK BASS OF THE NOETHBEN LAKES. 



Orystes nigricans : Agassiz. 



The color of this fish (which appears to vary with locality, 

 or the season) is generally dark olive-green on the back, 

 shading gradually into a brownish yellow on the sides ; belly, 

 opaque white. Body compressed, oval ; back arched ; belly 

 less curved than the superior outline; breadth as two to seven. 

 Lateral line concurrent with back. Head small, little less than 

 one-fourth the length of the body ; preopercle covered with 

 small scales, scales larger on opercle. The eye is on a line 

 between the snout and posterior angle of opercle, .one-third 

 distant from the snout, and is about five-eighths of an inch in 

 diameter ; the irides are dark brown above, and pale yellow 

 below. Nostrils small, double. Tongue toothless; both jaws 

 with small brushlike teeth, small patches of the same on 

 each side of the pharynx, as well as on the branchial arches. 

 Branchial rays seven. The first dorsal fin has ten sharp 

 spines, the anterior ray being short; the second dorsal is 



