64. GASTEEOSTEID.E GASTEROSTEITS. 393 



19S.— GASTEROSTEUS Linnams. 



StieklebacJcs. 



(Artedi; Linnseas, Syst. Nat. x, 1758: typo Gasterostetis aculeatus L.) 



Sticklebacks with the iimomiuate 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- 

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

 regions, {yaazi^p, belly; oarioy, bone.) 



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

 l^erhaps of generic value : 



a. Gill-membranes posteriorly free from the isthmus. 



b. Dorsal si^ines 7-11, di vergeut ( Pijgosteus Brevoort) pnngitiu8. 



bb. Dorsal spines .5, in a right line {Eucalia Jordan) inconstans. 



aa. Gill-membranes not free from the isthmus ; body more or less mailed {GasteroNitiis). 



microccphalus, biaculeatua, atlcinai, aculeatus. 



a. Gill-merabranes posteriorly free from the isthmus. 

 b. Dorsal spines 7-11, divergent (/"//r/osfcrts* Brevoort). 



C26. C». pUGig^itaus L. — Nine-sjnuccl Sticklcbaclc. 



Olivaceous above, profusely puuctulate, 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 deej). Xo 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 div^ergeut, 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 

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

 its edges raised. Ventral spines moderatL', serrulate, tlieir length more 

 than one-third that of the liead. 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, i^orthern i)arts of Europe, Atlantic 

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

 species, found in both fresh and salt water. 



(LinnjDUs, Syst. Nat.; Gunther, i, 6: GasttroHteus occidtntalis Cuvior «fe Valenciennes, 

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



'Brevoort, MSS. Gill, Canadian Naturalist, August, 18(15: type Gasicrostcua occiden- 

 talis C. &\. =:Gaiilerostcttn puiKjiliuts L. {nvyi), rump; 66c£ov, bone.) 



