FISH OF ONTARIO. 73 



(79) Brook Stickleback. 



(Eucalia inconstans.) 



Body elongated, rather stout; the caudal peduncle without keel; skin 

 entirely smooth. The ventral spines and pubic bones are very small, the 

 latter concealed under the skin. The thoracic processes covered by the 

 skin, slender and widely separated. Dorsal spines short, nearly equal in 

 length, placed in a straight line, the anterior spines shortest. Ventral 

 spines small and serrated. 



D. III. to IV., I., 10; A. I., 10. 



Males in the breeding season jet black, tinged with coppery red. The 

 females and young are greenish, variegated with darker. 



Common in small streams and ponds, where it secretes itself among 

 water plants, ready at any moment to attack any small fish which 

 approaches its lair, or to dart upon passing insects small enough to become 

 its prey. 



This species is a nest builder and is particularly vigorous in the 

 defence of its eggs or young. It grows to a length of two and a-half 

 inches. 



Genus PVGOSTEUS. (Maxv-spixed Sticklebacks.) 



This genus is characterized by the presence of nine to eleven divergent 

 spines and by the weakness of its innominate bones. As in Eucalia, the 

 gill membranes form a broad fold across the isthmus. 



Ten-spined Stickleback. ( Pygosteus pungitius. ) 



(80) Ten-spined Stickleback. 



(Pygosteus pungitius.) 



Body elongate, somewhat compressed. The dorsal spines are all in 

 the same line in a furrow, but they diverge so as to form a zigzag series. 

 Pubic bone weak, lanceolate, not serrate ; ventral spines slender, pun- 

 gent, finely serrate above and below ; gill membranes free from isthmus 

 behind; gill rakers long and slender; caudal fin lunate, slightly emargin- 

 ate. 



D. IX. to XI., I., 9; A. I., 8. 



