TROUT PERCH. 899 
sprinkled, living arrow of the White Water; able to zigzag up the cata- 
ract ; able to loiter in the rapids, whose dainty meat is the glancing 
butterfly.” 
PA IND II YC OW 9 Te rs COMO) Lets) Doe Atel Is WO) Uy ae 
PERCHES. 
Body moderately elongate, somswhat compressed, the caudal peduncle long and slen- 
der ; head conical, pointed, naked; mouth small, horizontal; maxillary short, narrow, 
without supplemental bone, not reaching to the large eye; margin of upper jaw formed 
by premaxillaries alone, which are short and not protractile; teeth very small, villiform 
on premaxillaries and lower jaw only; tongue short, adherent; gill-membranes sepa- 
rate, free from the isthmus; pseudobranchix present; branchiostegals six; gill-rakers 
short, tubercle-like; opercle with entire edges; lower limb of the preopercle well de- 
veloped, the angle nearly a right angle, its inner edge with a raised crest ; bones of the 
head cavernous, as in Acerina and Ericymba; cranium with a raised crest, which does 
not extend to the occiput; scales moderate, rather thin, adherent, their edges strongly 
ctenoid ; lateral line continuous; dorsal short, median ; ventrals anterior, just in front 
of the dorsal, 8-rayed ; pectorals narrow, placed rather higher than usual; anal small; 
caudal forked ; adipose fin present, small; stomach siphona], with about 10 well devel- 
oped pyloric ceca; ova rather large, not falling into the abdominal cavity before exclu- 
sion ; air-bladder present ; small fishes of the fresh waters of the cooler parts of Amer- 
ica; a single genus, with probably but one species. The group is one of special interest, 
as it combines with ordinary salmonoid characters the structure of the head and mouth 
of a percoid, resembling notably the European genus Acerina. 
GENUS 54. PERCOPSIS. Agassiz. 
_ Percopsis, AGassiz, Lake Superior, 1850, 284. 
Salmoperca, THOMPSON, 1853. 
Type, Percopsis guttatus, Agassiz. 
Etymology, perke, perch j opsis, appearance. 
The characters of the genus are included above. ° 
103. PERcoPsIs GUTTATUS Agassiz. 
Trout Perch, 
Percopsis guitatus, AGASSIZ, Lake Superior, 1850, 286.—GUNTHER, Cat. Fish. Brit. Mus., 
vi, 207.— JORDAN, Man. Vert. 2d Ed., 1878, 270, 
Salmoperca pellucida, THOMPSON. 
Pale olivaceous, a silvery stripe along the lateral line, becoming obsolete forwards ; 
upper parts with obseure, round dusky spots made of dark points. Head slender and 
conical ; mouth small, subinferior, maxillary not nearly reaching front of orbit; caudal 
_ peduncle long and slender; peritoneum silvery; head 3 4-5 in length; depth about 
44; D.i1; A.8; Lat.1.50. Length about 6 inches, 
Habitat, Great Lake Region, extending southward to the Delaware, Ohio and Kansas ' 
Rivers ; abundant only in tributaries of the Great Lakes. 
