ROSENBLATT and BUTLER: THE RIBBONKISH GENUS DESMODEMA 



1964:321; in part, all but 10th, 12th, 13th of 



listed specimens (fig. 2 is D. lorum, fig. 3 is D. 



polystictum). 

 Desmodema polystictum, not of Ogilby. Berry and 



Perkins 1966:668. Fitch and Lavenberg 



1968:88. Miller and Lea 1972:87. 

 Desmodema polystictus, not of Ogilby. Radovich 



1961:18. 



Diagnosis. — A Desmodema with 106-111 total 

 vertebrae (21-25 precaudal and 46-50 before the 

 anus), 4-7 (usually 6) caudal rays, snout length 

 greater than eye diameter, an exceedingly long 

 attenuate tail in juveniles and adults (Figures 3, 

 7) and scales present in prejuveniles and small 

 juveniles. 



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

 Ventral profile of body almost straight, but with a 

 slight convexity back to anus, then tapering back 

 to elongate tail section. Dorsal profile rising 

 rapidly from snout tip to dorsal origin, then as- 

 cending more gently to maximum depth of body 

 about one-half to three-quarters of head length 

 behind head, then tapering back to tail. Tail ex- 

 ceedingly long and narrow, postanal length 

 three-quarters of standard length. Anus on ven- 

 tral midline. 



Head length 3.2-3.8 in snout- vent length, 1.2- 

 1.3 in greatest body depth. Eye moderate, equal to 

 or (usually) shorter than snout. Ascending proces- 

 ses of premaxillae ending over or behind rear 

 margin of eye. Dorsal origin just behind preopercle 

 to over middle of opercle, preceded by a horny 

 process representing pterygiophores of first six 

 dorsal rays. First few dorsal rays short, succeeding 

 rays becoming longer, with maximum height of fin 

 over and posterior to anus. Fin height decreases 

 gradually along tail, probably as reconstructed in 

 Figure 6. Pelvics absent, but with buried bases 

 still evident. Pectorals low, their bases horizontal. 

 Pectoral pointed, but tip frayed and broken in all 

 specimens. 



Color in alcohol tan. Dorsal fin clear, becoming 

 dusky, then black along tail. Caudal black. Pec- 

 torals clear. Iris dark with a golden ring around 

 pupil. In life, probably silvery with red tones dor- 

 sally and on the head, and with the fins red. 



Description of prejuvenile. — Ventral profile 

 sloping down from tip of lower jaw to pelvics, then 

 tapering convexly back to vent, then tapering 

 more sharply to beginning of tail, then straight. 



z 



LU 



> 

 I 



t 150 - 



O 

 2 



100 200 300 400 500 600 700 800 900 1000 1100 1200 

 STANDARD LENGTH (mm) 



FIGURE 7. — The regression of snout-vent length on standard 

 length in Desmodema . Open circles D. polystictum , closed circles 

 D. lorum. 



Usually a notch in outline at position of vent, 

 which is asymmetrical, opening on the left side. 

 Dorsal profile of head steep, almost vertical in 

 smaller specimens. Back curved, point of 

 maximum body depth just behind pelvic base. 

 Dorsal profile becomes straight along tail elonga- 

 tion. Tail long and thin, postanal length about 

 one-half of standard length. 



Head length 3.8-4.2 in snout-vent length, 1.8- 

 2.2 in greatest body depth. Eye about equal to 

 snout length. Because of the steepness of the 

 forehead, the ascending processes of the premaxil- 

 lae end over the anterior third of the eye. 



Dorsal origin over middle to posterior third of 

 eye. First five or six dorsal rays elongate, remain- 

 der of fin shaped much as in adult except that the 

 rays along the elongate tail are not as long. Pelvic 

 fins present, close together, origin under pectoral 

 base. Anteroposterior axes of pelvics parallel with 

 sides. Pelvics broken in all our material, but 

 reaching beyond anus in one specimen. Pelvic rays 

 flattened and bladelike basally, the first the 

 broadest, becoming filamentous distally. Minute 

 prickles along rays. Pectorals as in adults. 



Color in alcohol tan, a darker area on back over 

 and behind head, extending down over forehead 

 onto snout. A variably developed dusky streak 

 from lower margin of orbit down behind maxilla. A 

 dusky streak along throat to pelvic bases. Spotting 

 somewhat variable but spots becoming larger and 

 more widely spaced posteriorly and above midline. 

 Three of five specimens with two noticeably larger 



853 



