56 PAPERS FROM TORTUGAS LABORATORY vol. xxxiv 



Key to the Species 



a. Tail not prehensile; head not shaped like that of a horse, and not at 

 right angle to axis of body 

 b. Body strongly angulate, quadrate in cross section 



c. Snout of moderate length, about 2.4 in head; rings about 

 18 -j- 30; keels on snout and head distinctly serrate; body 



with grayish crossbands; snout abruptly white . Hippichthys albtrostris 

 cc. Snout very short, about 3.0 in head; rings 17 -f- 26 or 27; 

 keels on snout and head not serrate (in adults); body with- 

 out crossbands; snout not white H. brachycephalus 



bb. Body not very strongly angulate, usually not quadrate in cross 

 section 



d. Median lateral keel (lateral line) bent downward on last 

 two body segments and continuous with inferior lateral 

 keel of tail; D. 18 to 21, on 1 or i l / 2 -f- 4 or 5 rings; snout 



very short, 3.4 to 4.0 in head Syngnathus jonesi 



dd. Median lateral keel ending abruptly, generally on last body 

 ring, not continuous with inferior lateral caudal keel 

 e. Dorsal fin short, with 20 to 25 rays 



/. Snout curved upward slightly, short, 3.0 to 3.5 in 

 head; a light triangular spot behind eye; radiating 



lines on eye S. dunckfri 



if. Snout not curved upward, longer, about 2.0 in head; 

 light spot behind eye missing 

 g. Snout moderately long, 2.0 to 2.1 in head; eye 

 3.6 to 3.8 in snout; lower part of opercle with 



pale oblique lines S. robertsi 



gg. Snout rather longer, 1.8 to 2.0 in head; eye 4.0 



to 4.3 in snout; opercle plain, without pale lines . S. elucens 

 ee. Dorsal fin longer, with 27 or more rays 



h. Dorsal fin moderately long, with 27 to 33 rays, over 

 1 to 2 , / 2 -f- 4 to 6 rings; body rings 16 to 18 

 /. Keels of head and body rather prominent, dis- 

 tinctly beaded; rings 16 to 18 -j- 32 to 35; D. 27 

 to 29, over 1 Y 2 or 2 -f- 4 or 5 rings; female with 

 a narrow silvery half-bar on lower half of each 

 ring of trunk, male with silvery spots on in- 

 ferior lateral keel of trunk S. rousseau 



ii. Keels of head and body less prominent, smooth 

 (not beaded); rings 17 or 18 -j- 34 to 37; D. 27 

 to 33, over 1 to 2% + 5V2 to 6 rings; silvery 

 half-bars or spots on lower part of trunk miss- 

 ing S. fioridae 



hh. Dorsal fin very long, with 34 to 37 rays, over 3 or 



4 -\- 4 or 5 rings; rings 19 to 22 -j- 33 to 37 . . S. louisianae 

 aa. Tail prehensile; head shaped like that of a horse, at right angle to 



axis of body Hippocampus punctulatus 



