STICKLEBACK. 127 



which the Pipe-fishes and Sea-horses are related, iu spite of their 

 strangely modified gills (see fig. 61, p. 131). The Opah or 

 King-fish, though so different in appearance from the Sticklebacks, 

 would seem to be more closely allied to these than to any other 

 fishes. 



The family Lamprididse, constituting the division Selenichthyes Opah 

 of some authors, contains only the fish just mentioned, the Opah, 

 Lampris luna, Floor-case 27. This is a large fish, attaining 

 sometimes the length of four feet. The body is short and deep, 

 and laterally compressed ; it is covered with minute scales ; the 

 snout is short and the mouth toothless. The branchial apparatus 

 is fully developed, and the gills are of the ordinary pectinate 

 type. The fins are without spines. The pelvic fins have 

 numerous rays (15-17), and the pelvic bones are connected 

 with the coracoid bones, which are large and do not meet 

 ventrally. The coloration of the Opah is vivid, and the flesh 

 is considered choice. The fish is pelagic in habit and is widely 

 distributed, specimens having been taken in various parts of the 

 Pacific and North Atlantic Oceans, the Mediterranean, and off 

 the coast of England. 



The Sticklebacks (family Gastrosteidae) are small fishes, with stickle- 

 the dorsal fins armed with two or more spines and with the sides back, 

 of the body more or less protected by bony shields instead of 

 scales. The pelvic fins are abdominal in position ; each has 

 one spine and one or two soft rays; the pectoral fin has no 

 spine, the anal fin has a single spine. The mouth is toothed ; 

 the ribs are slender ; the anterior vertebrae are not enlarged or 

 only slightly elongated. 



The Sticklebacks are widely distributed over the northern seas 

 and fresh waters. Several are British. This family is by some 

 authorities grouped with the Centriscidse, Amphisilidae, Aulosto- 

 matidse and Fistulariidse to constitute the division Hemibranchii, 

 characterised by the possession of pectinate gills, more or less 

 reduced in number, with a complete opercular apparatus ; with 

 a small and terminal mouth and the post-temporal bone simple 

 and immovable. 



The common Stickleback of England (424) is Gastrosteus 

 aculealus, called also the Three-spined Stickleback from the fact 



