EUCALIA FIVE-SPINED STICKLEBACKS 223 



parts silvery; upper part of cheek 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 firmly united, 

 forming a lanceolate, keeled process which extends backward 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 collections, to the lakes of northeastern Illinois, the Calumet 

 River at South Chicago, and clear brooks in LaSalle county. 

 It is a northern species, ranging through the Dominion of 

 Canada from New Brunswick 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 Missouri as far south as Kansas. 

 It is confined to fresh waters, and prefers 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 

 apparatus 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 wholly filamentous algae, which had been 

 taken by four of the specimens in quantities to make it certain 

 that they were purposely eaten. The animal food was about 

 equally insects and crustaceans, the latter chiefly Entomostraca 

 and the former largely Chironomus larvae. These and specimens 

 of Cypris taken by one of these fishes are evidence that it feeds, 

 in part at least, upon the bottom. 



