FISH OF ONTARIO. 79 



Family ATHERINID^. (The Silversides.) 



Body rather elongate, somewhat compressed, covered with scales of 

 moderate or small size, which are usually, but not always, cycloid. No 

 lateral line; some scales often with rudimentary mucous tubes.. Cleft of 

 the mouth moderate. Teeth small, on jaws and sometimes on vomer and 

 palatines, rarely wanting-. Premaxillaries protractile or not. Opercular 

 bones without spines or serrature. Gill openings wide, the gill membranes 

 not connected, free from the isthmus ; gills four, a slit behind the fourth. 

 Pseudobranchise present ; gill rakers usually long and slender. Branchio- 

 stegals five or six. Dorsal fins two, well separated ; the first of three to 

 eight slender flexible spines, the second of soft rays; anal with a weak 

 spine, similar to the soft dorsal, but usually larger ; ventrals small, abdom- 

 inal, not far back, of one small spine and five soft rays ; pectorals moderate, 

 inserted high. Air bladder present. No pyloric caeca. Vertebrae numer- 

 ous, usually about 23 + 23 = 46; third and fourth superior pharyngeals 

 cooossified with teeth. All the species have a silvery band along the side ; 

 this is sometimes underlaid by black pigment. 



Genus LABIDESTHES. 



Jaws prolonged, both of which are produced into a short depressed 

 beak. The scales are small, their edges entire. 



(84) Silversides. Skipjack. 

 (Labidesthes sicculus.) 



Body very slender, elongate. Caudal deeply forked. 



D. IV. I., II ; A. I., 23. Scales on lateral line, 75, 



Colour, green, the fish in life translucent, upper parts dotted. A 

 very distinct silvery lateral band edged above with lead colour ; cheeks 

 silvery. Length, about four inches. 



This species is found in Lake Ontario, Lake Erie, and the Detroit 

 River, and may be generally distributed throughout the Great Lake region. 

 As a food fish for larger species it is important. 



Group PERCOIDEA. (The Perch-ijke Fishes.) 



A group of fishes of diverse habits and forms, but on the whole repre- 

 senting better than any other the typical Acanthopterygian fish. The 

 group is incapable of concise definition, or in general, of any definition at 

 all ; still most of its members are definitely related to each other, and bear 

 in one way or another a resemblance to the typical form, the Perch, or 

 more strictly to its marine relatives, the Sea Bass or Serranidae. The 

 following analysis gives most of the common characters of the group : 



