64. GASTEROSTEID^E GASTEROSTEUS. 393 



\ 



193. GASTEROSTEUS Linnaeus. 



Sticklebacks. 



(Artedi; Linnaeus, Syst. Nat. x, 1758: type Gasterosteus aculeatus L.) 



Sticklebacks with the iuuomiuate bones coalesceut on the median line 

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

 or lanceolate plate. Tail slender, keeled or not. Skin naked or variously 

 covered with bony plates. Dorsal spines 2-10 in number, variously de- 

 veloped. Species numerous. Fresh waters and shores of all northern 

 regions, (jaar^p^ belly; da-iov, bone.) 



The group may be divided into the following sections, which are 

 perhaps of generic value : 



a. Gill-membranes posteriori}' free from the isthmus. 



b. Dorsal spines 7-11, divergent ( Pygosteus Brevoort) pitngitivs. 



bb. Dorsal spines 5, in a right Hue (Euculia Jordan) incoaistans. 



aa. Gill-inembrauesuot free from the isthmus ; body more or less mailed ( Gasterositus). 



microccphalus, biaculealus, atkiusi, aculeatus. 



a. Gill-membranes posteriorly free from the isthmus. 

 b. Dorsal spines 7-11, divergent (Pygosteus* Brevoort). 



626. O. pungitius L. Nine-spined Stickleback. 



Olivaceous above, profusely punctulate, irregularly barred with darker, 

 silvery below. Body very slender, somewhat compressed, tapering into 

 the very long and slender caudal peduncle, which is much depressed and 

 strongly keeled, broader than deep. No dermal bony plates ; skeletal 

 plates not all covered by skin. Post-pectoral plate well developed, 

 striated. Head shortish, the snout rather blunt. Thoracic processes 

 well developed, widely divergent, forming a U-shaped figure Dorsal 

 spines moderate, the anterior diverging to the right or left at various 

 angles, the posterior more nearly erect. Anal spine large, larger than 

 the dorsal spines. Innominate bone feeble, lanceolate, not carinated, 

 its edges raised. Ventral spines moderate, serrulate, their length more 

 than one-third that of the head. Gill-rakers long and slender; gill- 

 membranes free from the isthmus posteriorly. Head 4; depth 5-G. 

 D. IX, I, 9 ; A. I, 8. L. 3 inches. Northern parts of Europe, Atlantic 

 coasts of America, Great Lakes, and northward; a widely distributed 

 species, found in both fresh and salt water. 



(Linniens, Syst. Nat.; Guuther, i, 6: Gasterosteus occidtntalis Cuvier & Valenciennes, 

 iv, 509 : Gasterosteus dckayi Agassiz, Lake Superior, 311 (Massachusetts) : Gasterosteus 



* Brevoort, MSS. Gill, Canadian Naturalist, August, 18H5: type Gasterosteus occiden- 

 taliti C. & V. = Gasterosteus punyitiux L. (nvyi/, rump; o6cEov, bone.) 



