224 REPORT OF NEW JERSEY STATE MUSEUM. 



dorsal, with a single spine. Pectorals rather short, unusually 

 far behind gill-openings. Caudal narrjow, usually emarginate. 

 Ventral fins sub-abdominal, consisting of a stout spine and i or 

 2 rudimentary rays. 



Small fishes of the fresh waters and the arms of the seas in 

 northern regions. Noted for their pugnacity, exceedingly de- 

 structive to the spawn and fry of larger fishes. Most build elab- 

 orate nests, which the male defends with spirit. They are ex- 

 tremely variable and are apparently readily affected by changes 

 in their surroundings. 



Key to the genera. 



a. Gasterostein^. Pubic bones fully joined, forming a triangular or lan- 

 ceolate plate on median line of belly behind and between ventrals. 

 h. Gill-openings confluent, membranes forming a broad free margin across 

 isthmus ; dorsal spines VIII to XI, divergent ; skin naked or nearly 



so. PYGOSTEUS 



hh. Gill-openings restricted, membranes mesially united to isthmus ; dorsal 



spines XI, free ; skin mailed, partly mailed, or naked. gasterosteus 



aa. Apeetin^, Pubic bones widely separated posteriorly, forming a bony 



ridge on each side of abdomen between which are ventral fins ; dorsal 



spines IV, divergent ; sides not mailed, apeetes 



Genus Pygosteus Gill. 



The Nine Spined Sticklebacks. 



Pygosteus pungitius (Linnaeus). 



Ten Spined Stickleback. Alany Spined Stickleback. 

 Stickleback. 



Head 3J/2 ; depth 5>< ; D. X, I, 9; A. I, 10; length of caudal 

 peduncle ij^ in head; length of caudal ij/s', pectoral i}i] ven- 

 tral spine 2^ ; snout sy2 in head, measured from tip of upper 

 jaw; eye 3^ ; maxillary 33/^ ; interorbital space 4^. Body very 

 slender, compressed, and tapering into long, slender caudal 

 peduncle, which is strongly keeled, broader than deep, and much 

 depressed. Head compressed, rather attenuate, and upper profile 

 sloping a little more than lower. Snout rather conic. Eye 



