98 FISHES OF PENNSYLVANIA. 


ORDER HEMIBRANCHIT (THE HALF-GILLED FISHES). 
Famity GASTEROSTEIDA: (Tue Srickiesacks. ) 
Genus EUCALIA Jorpay. 
110. Eucalia inconstans (Krrrianp). 
The Brook Stickleback. 
The body is more elongate than in the other sticklebacks described, and stouter; 
the caudal peduncle has no keel and the skin is entirely smooth. The ventral 
spines and pubic bones are very small, the latter concealed under the skin. “The 
thoracic processes are covered by the skin, slender and widely separated. The dor- 
sal spines are short, nearly equal in length, placed in a straight line; the anterior 
spines shortest. The ventral spines are small and serrated. The depth equals one- 
fourth and the depth two-sevenths of the total length without caudal. 
DAkb-LV, {DAO cA. 15.20: 
Males in the breeding season are jet black, tinged entirely with coppery red. The 
females and young are greenish, variegated with darker. 
The brook stickleback occurs in the freshwaters from New York west- 
ward to Dakota and is said to extend north to Greenland. A variety 
from Cayuga Lake has been described by Dr. Jordan. It has the ven- 
tral spines longer than the pubic bones. 
In Pennsylvania the brook stickleback inhabits the Ohio valley. It 
grows toa length of two and one-half inches and has no value as food, 
but is an interesting aquarium fish. It is, however, extremely pugna- 
cious and when kept in confinement great mortality is caused by its 
quarrels. The species is abundant in small streams, where it secretes 
itself among aquatic plants and is always on the alert for an attack upon 
small fishes andinsects. Specimens have recently been obtained from an 
artesian well in South Dakota, the well having adepth of seven hundred 
feet. From thisgreat depth the fish were brought up in full strength and 
vigor and were kept in an aquarium several monthsatterwards. Asimilar 
occurrence has been recorded by Mrs. Eigenmann in the Proceedings of 
the National Museum for 1883, p. 217, of Williamson’ stickleback at San 
Bernardina, Cal. The well in this case was only one hundred and ninety- 
one feet deep. There is no doubt that the fish reach the wells through 
streams which become subterranean in a certain part of their course. 
This species is a nest builder and is vigorous in the defense of its 
eges and young. 
Genus GASTEROSTEUS (Artep1) Linyzvs. 
111. Gasterosteus aculeatus Linyzvus. 
The Two-spined Stickleback. 
The body is fusiform, moderately elongate and compressed ; the caudal peduncle 
is short and slender and distinctly keeled. The height of the body is less than 
