ROSENBLATT and BUTLER: THE RIBBONFISH GENUS DESMODEMA 



FIGURE 4.— Prejuveniles ofDesmodema. Upper figure D. lorum, LACM 30597-1, 87 mm SV, 188 mm SL. Lower figure D. polystictum, 



SIO 75-55, 88 mm SV, 125 mm SL. 



lorum. Fourmanoir 1969:36. Legand et al. 

 1972:383. 

 Trachipterus trachyurus, not of Poey. Leapley 

 1953:236; Fort Lauderdale, Fla. 



Diagnosis. — A Desmodema with 71-74 total 

 vertebrae (18-20 precaudal and 37-42 before the 

 anus), 7-10 (usually 8) caudal rays, snout length 

 less than eye diameter, attenuate tail in juveniles 

 and adults (Figures 3, 7), and scales absent at all 

 sizes. 



Description of adult (see also Tables 1-3). — 

 Ventral profile of body almost straight to anus, 

 then tapering to elongate tail. Dorsal profile rising 

 in a gentle curve to a point a little less than 1 head 

 length behind head, then tapering rapidly to a 



point about IV2 head lengths behind anus, then 

 tapering more gradually along elongate tail sec- 

 tion. Tail long and straplike, postanal length al- 

 most two-thirds of standard length. Anus on vent- 

 ral midline. 



Head 2.2-2.5 in snout- vent length, and about 1.3 

 in greatest body depth. Eye large, diameter 

 slightly greater than snout length. Ascending pro- 

 cesses of premaxillae extending back to a point 

 over posterior third of eye. 



Dorsal origin over preopercle, preceded by a 

 thickening representing pterygiophores of first six 

 dorsal rays of juveniles. First fin rays short, suc- 

 ceeding rays becoming rapidly longer to about 

 point of maximum body depth, height of fin then 

 increasing more slowly, with longest rays slightly 

 before anus. Behind level of anus fin rays become 



849 



