MORONE WHITE PERCH 321 



species, both American, one inhabiting fresh waters of the Misssissippi 

 Valley and the other brackish waters and the mouths of rivers of the 

 Atlantic coast. 



MORONE INTERRUPTA Gill 

 (yellow bass) 



Gill, 1860, Proc. Ac. Nat. Sci. Phila., 118. 



j. &G., S30; M. V., 137; B., I, 127 (mlssissipiensis) ; J. & E., I, 1134; N., 36; J., 44; 

 F., 63 (Roccus); F. F., I. 3, 37; L., 29. 



Length 12 to 18 inches; body rather deep and compressed and back 

 elevated; profile angled at nape; depth 2.7 to 2.9; greatest width about 

 2 in greatest depth; depth caudal peduncle 1.4 to 1.6 in its length. 

 Ground color olive-buff, with many small indistinct punctulations of 

 emerald ; alternate rows of scales on sides with dark greenish to blackish 

 central bands, these adjoining to form prominent longitudinal stripes, 3 

 above lateral line, one (which is more or less moniliform) coincident with 

 it, and 3 or 4 below lateral line; stripes below lateral line interrupted on 

 posterior part of body, the breaking point sometimes indicated by irreg- 

 ularly disposed black spots ; ventral region lighter than sides but of simi- 

 lar colors ; vertical fins with considerable bluish tinge ; cheeks and opercles 

 with bluish and emerald iridescence; pupil pale dark blue; iris light green- 

 ish above pupil, darker outward. Head subcpnic, pointed, 3 to 3.2 in 

 length; width of head 2 to 2 . 1 in its length; interorbital space little con- 

 vex, 4 to 4 . 7 ; nose 3 . 1 to 3 . 7 ; mouth terminal, slightly less oblique than 

 .in last species; maxillary barely to middle of 6rbit, 2.6 to 2 . 8 in head; 

 lower jaw not sensibly projecting; gill-rakers longer than branchial fila- 

 ments" X + 13 to 16. Dorsal IX-I, 12 ; longest spine 1 . 6 in head; base of 

 soft dorsal about 1 .4 in base of spinous; caudal forked; anal III, 10, the 

 spines not graduated, the first usually less than J of second, the second 

 and third of about equal length ; ventrals § to vent; pectorals 1 . 5 to 1 . 6. 

 Scales 7, 51-55, 10-12, strongly ctenoid ; lateral line complete or nearly 

 so, scarcely arched anteriorly, somewhat flexubse; cheeks and opercles 

 fully scaled, rows 12. 



This species is distributed in Illinois much like the white bass, 

 and although nearly twice as abundant in our collections as that 

 species, it comes everywhere from similar waters — that is, from the 

 large rivers and adjacent lakes. It is primarily a lake species, our 

 one hundred and two collections giving us a frequency coefficient of 

 3. 16 for bottom-land lakes and sloughs, and of 1 .82 for rivers of 

 the largest size. But two of these collections were from creeks or 

 the smaller rivers. We have found it, like the preceding species, 

 much more abundant in central Illinois than in either of the other 

 sections, and about equally frequent in the Illinois River and in the 

 Mississippi. 



