96 ' TELEOSTEI : HEMIBKANCHII. — XVIII. 



sal nor ventral fins ; caudal small or wanting ; anal minute, of 1 or 

 2 rays; tail long. Male (ishes with an egg-pouch, usually placed 

 on under side of tail and formed of two folds of skin which meet on 

 the median line. The eggs are received from the female into this 

 pouch, and retained for some time after hatching, when the pouch 

 opens and the young, then £ to \ inch long, escape. Genera about 

 14 ; species 150, in all warm seas, (avv, together; yvddos, jaw.) 



a. Axis of head in a line with axis of body. (Syngnathince.) 

 b. Humeral bones united below; C. present; P. well developed; D. oppo- 

 site vent; shields not spinous Siphostoma, 105. 



aa. Axis of head forming an angle with axis of body; the head and neck 

 horse-shaped, or like that of a "Knight" at chess. (Hippocampince.) 

 c. Body compressed ; occiput with a narrow, bony crest, surmounted 

 by a --tar-shaped coronet ; shields tubercular or spinous ; egg-sac 

 in male at base of tail, which is prehensile and without fin. 



Hippocampus, 106. 



105. SIPHOSTOMA Rafinesque. Pipe-fishes, (alcjiau, tube ; 



(TTOfia, mouth.) 



235. S. fuscum (Storer). Common Pipe-fish. Top of head 

 slightly keeled; D. covering 4 body rings and 5 behind vent; rings 

 18 to 20 -\- 36 to 40 ; dorsal rays 36 to 40; snout moderate. Head 

 9 ; L. 7. Olivaceous, sides mottled. Newfoundland to Va., com- 

 mon. Numerous other species occur S. (Lat., dusky.) 



106. HIPPOCAMPUS Rafinesque. Sea Horses. 



(These small fishes inhabit grassy bays and often the open sea 

 in warm regions. They are wont to twist the very prehensile tail 

 around pieces of floating sea-weed or eel-grass. They are thus often 

 drifted to great distances in the sea. The species are very simi- 

 lar to each other, and not easily distinguished.) (Ancient name 

 from t7r7ro?, horse, and KafxTros, a wriggling creature.) 



236. H. hudsonius DeKay. Sea Horse. Dusky, unspotted, 

 but with grayish blotches, edged with blackish; D. with dark band; 

 snout 1| in head ; spines on head weak, with cirri ; spines all blunt- 

 i-h. D. 19, on 3^ of the 11 body rings. L. 6. Cape Cod to Fla., 

 not common. Several other species occur S. 



Order XVIII. HEMIBRANCHII. (The Half-gilled 



Fishes.) 



Gills normal, but the branehihyals and pharyngeals reduced in 

 number; V. more or less abdominal. A small group of 5 or 6 fam- 

 ilies, intermediate between the Lophobranchii and the true Acan- 

 thopteri. (rjfii-, half; ftpdyxia, gills.) 



