322 contributions to north american ichthyology iv. 



Family XLVII.— PERCOPSID^. 



{The Trout Perches.) 



Body moderately elongate, somewhat compressed, the caudal pedun- 

 cle long and slender. Head conical, pointed, naked. Mouth small, 

 horizontal; maxillary short, narrow, without supi)lemental bone, not 

 reaching to the large eye 5 margin of upper jaw formed by premaxilla- 

 ries alone, which are short and not protractile. Teeth very small, villi- 

 form on premaxillaries and lower jaw only. Tongue short, adherent. 

 Gill-membranes separate, free from the isthmus. Pseudobranchiae pres- 

 ent. Branchiostegals 6. Gill-rakers short, tubercle-like. Opercle with 

 entire edges. Lower limb of the preopercle well developed, the angle 

 nearly a right angle, its inner edge with a raised crest. Bones of the 

 head cavernous, as in Acerina and Ericymha. 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 siphonal, 

 with about 10 well-developed pyloric coeca. Ova rather large, not fall- 

 ing into the abdominal cavity before exclusion. Air-bladder present. 

 Small fishes of the fresh waters of the cooler parts of America ; a sin- 

 gle 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. 



{Percojjsidw Giinther, vi, 207.) 



152.— PEKCOPSIS Agassiz. 

 Trout Perch. 

 (Agassiz, Lake Superior, 1850, 284: type Percopsis guttatus Ag.) 



Characters of the genus included above, (^e/^zij, j^erch; 6<,''tc, appear- 

 ance.) 



519. P. giittatMS Agassiz. 



Pale olivaceous, a silvery stripe along the lateral line, becoming ob- 

 solete forwards ; upper parts with obscure round dusky spots made of 

 dark points. Head slender and conical. Mouth small, subinferior, 

 maxillary not nearly reaching front of orbit. Caudal xieduncle long and 



