270 FISHES. 



/ 



SUB-OKDER-ISOSPOKDYLI. 



(The Trout-like Fishes.) 



FAMILY CIV. PERCOPSID.E. 



(The Trout Perches) 



Body covered with moderate-sized ctenoid scales; head 

 naked; no barbels; opercles well developed; gill open- 

 ings wide; an adipose fin; jaws with villiform teeth; no 

 teeth on vomer or palate; margin of upper jaw formed 

 by intermaxillaries alone ; branchiostegals six. A single 

 genus and one or two species inhabiting the fresh waters 

 of the northern U. S. Interesting little fishes, with the 

 general characters of Salmonidce, but having the mouth 

 and scales decidedly Perch-like. 



/. PERCOPSIS, Agassiz. TKOTTT PERCHES. 

 1. P. guttatus, Ag. Depth 4 in length; head 3f ; 

 silvery, almost pellucid; upper parts with rounded dark 

 spots made up of minute dots; D. 11; A. 7; L. 10; 

 Great Lakes; Ohio R. (Jordan)', Potomac R. (Baird)\ 

 Delaware R. (Abbott.) 



FAMILY CV.-SALMONID^E. 



(The Trout.) 



Head naked, body scaly, no barbels; margin of upper 

 jaw formed by intermaxillaries mesially and by maxil- 

 laries laterally; adipose fin present; belly rounded; air 

 bladder large, simple; pseudobranchiae present; pyloric 

 appendages usually numerous; eggs falling into the 

 cavity of the abdomen before exclusion. Fresh waters 

 of northern regions, many species periodically descend- 

 ing to the sea; a few permanently marine. 



Genera sixteen; species one hundred and sixty. The 



