64. GASTEROSTEID.E GASTEROSTEUS. 
393 
193.— OASTEROSTEUS Linnajus. 
SticJclebaclcs. 
(Artecli; Linnaeus, Syst. Nat. x, 1758 : type Gasterosteua aculeatua L.) 
Sticklebacks with the innominate bones coalescent on the median line 
of the belly, behind and between the ventral tins, 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 niimerons. Fresh waters and shores of all northern 
regions, {yaffzrjp, belly j oV-fov, bone.) 
The group maj'^ be divided into the following sections, which are 
perhaps of generic value : 
a. Gill-membranes posteriorly free from the isthmus. 
b. Dorsal spines 7-11, divergent {Pygosteus Bveyoort) pnngitius. 
bb. Dorsal spines 5, in a right line (A’aca/ia Jordan) incanatans. 
aa. Gill-membranes not free from the isthmus ; body more or less mailed ( Gasterosieus). 
microecpbulus, biaculcatus, atkinai, aculeatua. 
a. Gill-membranes posteriorly free from the isthmus. 
b. Dorsal spines 7-11, divergent (Pyyostc’as * Drevoort). 
G26. G. pasng^itius L. — Nine-sinned Stieldcbacic. 
Olivaceous above, profusely puuctulate, irregularly barred with darker, 
silvery below. Body very slender, somewhat comjiressed, 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 
siiines 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 
s])ecies, found in both fresh and salt water. 
(Linmsus, Syst. Nat.; Gunther, i, 6: Gaateroateua occidenfalis Cuvier & Valenciennes, 
iv, 5U9 : Gaateroateua dvlcayi Agassiz, Lake Superior, 311 (Massachusetts) : Gaateroateua 
*Brevoort, MSS. Gill, Canadian Naturalist, Ai^gust, 18G5: typo Gaaierosteus occiden- 
talia C. &Y. — Gaateroateua pungitina h, (zrny?/, rump ; (3d r£ 0 »', bone.) 
