74 CHECK LIST OF THE 



Colour brownish above, punctulate and irregularly barred with black. 

 Tail keeled. Length about three inches. In the breeding season the male 

 becomes rosy beneath. 



Not particularly common in this Province, but generally distributed 

 through the region of the Great Lakes. It is said to be abundant in the 

 streams of the Atlantic coast and in the fresh waters of the Arctic regions. 



GENUS GASTEROSTEUS. 



Sticklebacks with the innominate bones coalescent on the median line 

 of the belly, behind and between the ventral fins, forming a triangular or 

 lanceolate plate. Gill membranes united to the isthmus ; tail slender, and 

 usually keeled ; skin variously covered with bony plates ; dorsal spines 

 strong, with nondivergent bases. Species numerous and highly variable, 

 those found in the sea usually with the body completely mailed, the fresh 

 and brackish water forms variously mailed, or even altogether naked. 



5 A 



Two-spined Stickleback. ( Gasterotteus bispinoaus. ) 



(81) T\vo=spined Stickleback. 



(Gasterosteus bispinosus.) 



Body fusiform, moderately elongate and compressed ; caudal peduncle 

 short, slender and distinctly keeled. The sides are covered with about 

 thirty-three bony plates. The processes from the shoulder girdle cover 

 the breast except a small naked area between them. At the base of each 

 dorsal spine is a large rough bony plate to which the spine is hinged in 

 such a way that it may be fixed and immovable at the will of the fish. The 

 pelvic bone is lanceolate. The spines are all closely serrated, those in 

 front of the anal and soft dorsal smallest. At the base of the ventral spine 

 there is a cusp. 



D. II. I., ii to 13; A. I., 9. 



Colour, greenish olive, lighter on the sides, lower parts silvery. Gill 

 covers silvery, with dusky markings; iris silvery; pupil black; fins pale. 



