248 FISHES. 



articulated with the preopercle ( as in Cottidoe^ with 

 which these fishes were formerly associated) ; skin naked 

 or with bony plates; dorsal preceded by two or more 

 isolated spines; ventrals abdominal, of a stout spine, 

 accompanied by a rudimentary ray ; air bladder simple ; 

 a few pyloric cceca. Genera about four; species twenty- 

 five or less, in fresh waters and arms of the sea in north- 

 ern Europe and America. 

 * Dorsal with 2 to 6 free spines. 

 f Sides mailed ; a serrated bony ventral cuirass and usually a 



bony caudal keel GASTEROSTEUS, 1. 



ft Sides naked ; no caudal keel ; ventral cuirass reduced, not 



serrated. 



\ Dorsal spines not in a right line when erected, the anterior 



ones highest; ventral plates 2 not on median line; 



caudal peduncle very slender. . . APELTES, 2. 



\\ Dorsal spines in the same line, the lowest in front ; ventral 



plate single, on the middle line of abdomen ; caudal 



peduncle stouter EUCALIA, 3. 



** Dorsal spines 7 or more ; sides mailed or not. PYGOSTEUS, 4. 



/. GASTEROSTEUS, Linnaeus. MAILED STICKLEBACKS. 

 1. G. noveboracensis, C. & V. NEW YORK STICKLE- 

 BACK. Maine to Cape Hatteras, coastwise; sometimes 

 ascending streams. 



2. APELTES, DeKay. NAKED STICKLEBACKS. 



< GasterosteuS) L. 



1. A. quadracus, (Mitch.) Brevoort. FOUR-SPINED 

 STICKLEBACK. Abundant, with the preceding. 



3. EUCALIA, Jordan. NEST - BUILDING STICKLEBACKS. 



< Apeltes^ Authors. 



1. E. inconstans, (Kirtland) Jordan. BROOK STICKLE- 

 BACK. OHIO STICKLEBACK. Head about 3^ in length ; 



