EUCALIA — FIVE-SPINED STICKLEBACKS 223 



and opercle crossed by a splash of bright green; median fins more or 

 less dusky; spring males said to be jet-black, tinged with red anteriorly. 

 Head 3.2 to 3.8; width of head 1.9 to 2 . 3 in its length ; interorbital 

 space 4.6 to 5.7; eye 3.2 to 3.4; nose 4 to 5; mouth small and very 

 oblique, the maxillary considerably short of front of orbit, 4 to 4 . 8 in 

 head. Dorsal V (or VI), 9-10, the spines in a right line, not divergent; 

 caudal subtruncate (scarcely lunate in our specimens) ; anal rather large, 

 I, 9 or 10, the spine shorter than the anterior rays; ventrals with a short 

 but strong and sharp spine with minute serratures, its length 3 . 5 to 4 

 in head; pectorals 1 . 7 to 2 in head; post-pectoral plate present; thoracic 

 processes slender and covered with skin, widely separated; pubic bones 

 fimilv united, forming a lanceolate, keeled process which extends back- 

 ward from between ventrals. Skin smooth, destitute of dermal plates. 



This little stickleback, one of the hardiest, most combative, and 

 most individual of our smaller fishes, has been confined, in our col- 

 lections, to the lakes of northeastern Illinois, the Calumet River at 

 South Chicago, and clear brooks in La Salle county. It is a northern 

 species, ranging through the Dominion of Canada from New Bruns- 

 wick to Calgary on the branches of the Saskatchewan, and thence 

 through the St. Lawrence, Lake Champlain, and the Great Lakes 

 from Ontario to Superior, to central Ohio and the basin of the Mis- 

 souri as far south as Kansas. It is confined to fresh waters, and pre- 

 fers clear cool brooks. This species builds nests, like the others of 

 its family. In the aquarium it is quarrelsome, and destructive even 

 to fishes of larger size. 



Its mouth is small, its gill-rakers are long and slender, about half 

 the length of the corresponding filaments, and its pharyngeal appa- 

 ratus is insignificant. The intestine is short and simple, not longer 

 than the head and body together. Notwithstanding this equipment 

 for a carnivorous life, five specimens examined by us were found to 

 have fed on plants and animals in equal quantities — the former 

 wholl}^ filamentous alg^, which had been taken by four of the speci- 

 mens in quantities to make it certain that they were purposely eaten. 

 The animal food was about equally insects and crustaceans, the lat- 

 ter chiefly Entomostraca and the former largely Chironomus larvae. 

 These and specimens of Cypris taken by one of these fishes are evi- 

 dence that it feeds, in part at least, upon the bottom. 



