PERCA FLAVESCENS. 3 



placed midway between the eye and snout ; the posterior is oval, and both are on 

 a line within the orbit. The eye is very large, and is longest in the horizontal 

 direction ; its posterior margin is equidistant between the angle of the opercle 

 and the snout, and its inferior margin is about the median plane of the head ; 

 the lower jaw, though apparently longer than the upper when the mouth is open, 

 is in fact shorter, and received within it when the mouth is shut. 



The mouth is large, though the posterior margin of the upper jaw scarcely ex- 

 tends beyond the orbit ; the upper jaw, the margin of which is made up entirely 

 of the inter-maxillary, is armed with a large band of rough, villiform, equal teeth, 

 and the inferior maxillary has a narrower band of similar teeth ; there is a nar- 

 row chevron-like group on the anterior extremity of the vomer, and a more slen- 

 der band on each palatine, as well as a few minute teeth on the transverse bones, 

 where they join the vomer; the internal faces of the branchial arches are fur- 

 nished with rows of minute teeth, and the pharyngeal bones are armed in a 

 similar manner ; the tongue is thin, rounded in front, smooth, and tolerably free. 

 There are seven branchial rays. 



The pre-opercle is rounded at its angle, and is serrated in nearly its Avhole free 

 margin, both behind and below, where the serratures are largest and directed 

 forward; it is naked or uncovered with scales. The opercle is sub-triangular, 

 pointed and spinous behind, Avith its upper side rounded ; it is naked or without 

 scales on its lower half, which is marked with radiating strise more or less distinct. 

 The sub-opercle is sub-triangular, with its apex behind and its inferior border 

 rounded and serrated, and is covered with scales. The inter-opercle is broad, and 

 rounded below. The head above in front of the eye is smooth ; the cheeks are 

 covered Avith scales. 



The dorsal fin is double, or is so deeply cleft as to appear so, the connecting 

 membrane between the two portions being so slightly elevated. The anterior is 

 long, and is equal in elevation to more than half the height of the body ; it 

 begins just behind the opercle, and has sixteen spines, partially received in a 

 groove when the fin is closed ; of these spines the first is short, and the third, 



