322 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY - IV. 



FAMILY XLVIL PERCOPSID^. 



(The Trout Perches.} 



Body moderately elongate, somewhat compressed, the caudal pedun- 

 cle long and slender. ITead conical, pointed, naked. Month small, 

 horizontal; maxillary short, narrow, without supplemental bone, not 

 reaching to the large eye ; margin o upper jaw formed by premaxilla- 

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

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

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

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

 entire edges. Lower limb of the prcopercle well developed, 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 lino continuous. 

 Dorsal short, median ; ventrals anterior, just in front of the dorsal, 

 S-rayed; pectorals narrow, placed rather higher than usual 5 anal 

 small; caudal forked; adipose fin present, 'small. Stomach siphoual, 

 with about 10 well -developed pyloric cceca. 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. 



(I'crcopuidce Giinthcr, vi, 207.) 



152. PERCOPSIS Agassiz. 

 Trout Perch. 



(A;, r .-i-M/, T.:iKc Superior, l-r,n, -j- 1 : type Peroopris gwtttthu Ag.) 



Characters of the genus included above. (-J/JXTJ, perch ; <;</''-> appear- 

 ance.) 



519. P. Kiitfatios 



Pale olivaceous, a sihery 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 peduncle long and 



