SHORT BIGEYE IN WESTERN NORTH ATLANTIC 



131 



Figure 19. — Juvenile Pseudopriacanthus altus, 67.3 mm. standard length (UF 1434). 



Dorsal Jin. — The dorsal fin was immaculate in 

 specimens up to 5.3 mm. The soft part of this 

 fin continued immaculate in specimens up to 12.1 

 mm. (fig. 11) and in some to as large as 16.5 mm. 



The interspinous membranes received pigment 

 the earliest, and this was first noted in a 6.6-mm. 

 specimen (fig. 10). The numerous pigment spots 

 occupied tlie middle half of the membranes con- 

 necting the first seven spines of the fin. At 8.2 

 mm. pigment was present over the entire spinous 

 fin, with the exception of the tips.^ This pigment 

 pattern intensified, especially along the edges of 

 the spines, until in u 10.2-mm. specimen the fin 

 appeared very dark. 



In a 12.1-mm. individual, unpigmented disk- 

 shaped areas had begun to form on tiie spines and 

 adjacent membranes, half on spine and half on 



' In preserved material the clear tips of the interspinous membranes often 

 were torn away, sivinc the impression of color extendinB to the edcc of the 

 fln— not to he confused with the apparently normal loss of the membranous 

 flaps at the tiris of the spines, which occurs with change of habitat, or at ap- 

 proximately 50-60 mm. 



membrane, about midway of each spine (fig. 11). 

 These clear areas, seemingly formed by the migra- 

 tion of pigment, formed a row of spots parallel 

 to the base of the fin. The pigmented edges of 

 these light spots were darker than the adjacent 

 membrane, probably due to the migration and 

 consequent crowding of the pigment as it retreated 

 to form the unpigmented area. Also at about 12 

 mm. pigment had begun to appear at, and ad- 

 jacent to, the base of the soft part of the dorsal, 

 covering progressively less of the posterior soft- 

 rays and their membranes (fig. 11). 



At 15.0 mm. (fig. 12), tiie unpigmented spots in 

 the initial row on the spinous dorsal had become 

 more prominent and a second series of spots had 

 begun to form distally and parallel to them. The 

 tii)s of the s])ines and nieinbrane at the tips re- 

 maiiKMl impigmcnted. Also at 15.0 mm. single 

 chroniat()j)iiores had l)egun migrating along the 

 soft rays (but not along the membranes) from the 

 ])ignient nt tlie base of the soft fin. 



