sally as deeply embedded pigment at the nape. With 

 continued development the melanophores form a solid 

 sheath on the peritoneum surrounding the gut. 



Melanophores appear at the posterior margin of each 

 pectoral fin in some larvae as small as 4.0 mm. About 

 half the larvae examined between 4.0 and 5.0 mm have 

 this posterior margin of fine melanophores and the pig- 

 ment is present in all larvae in the 5.0- to 11.0-mm range. 

 The melanophores are then lost, and almost all larvae 

 larger than 11.0 mm have unpigmented fins. 



Melanophores appear on the posterior lobes of the 

 brain in 5.2- to 7.0-mm larvae and are present in all lar- 

 vae larger than this. They also appear above the anterior 

 lobes of the brain in larvae between 7.0 and 9.0 mm in 

 length and in most larvae larger than 9.0 mm. 



Pigmentation of the pelagic juveniles of the two species 

 is markedly different. It begins to appear in some 

 specimens of S. altivelis of the 14- to 20-mm size range. 

 On the head, patches of melanophores appear on the 

 opercle, cheek, snout, and jaws. In most specimens larger 

 than 22 mm, the patches are confluent, and the head is 

 generally dusky with darker areas at the opercle and 

 along the upper jaw. 



A patch of melanophores appears superficially over 

 each side of the gut in specimens as small as 14 mm. 

 These patches expand to form a solid melanistic sheath 

 in some specimens of the 14- to 20-mm size range. The 

 posterior margin of the sheath is an arc running from the 

 vent to the nape and stands out sharply against the pig- 

 mentless region of the trunk posterior to the sheath. With 

 continued development the pigment sheath expands 

 posteriad and is a striking feature of the pelagic 

 juveniles. In the 20- to 30-mm size range the sheath ex- 

 tends posteriad to a vertical from the first or second anal 

 fin spines. In the 30- to 40-mm size range the sheath ex- 

 tends posteriad to the 2nd or 3rd anal spine in most 

 specimens and to the soft dorsal fin in some. In most 

 pelagic juveniles of the 40- to 50-mm size range, the 

 dusky sheath extends back to the soft dorsal and it does 

 so in all specimens of the 50- to 60-mm size range. When 

 the juveniles become benthic, the dusky sheath extends 

 posteriad to the caudal fin. 



The fins become deeply and characteristically pig- 

 mented in juveniles of S. altivelis. The anterior portion of 

 the spinous dorsal fin becomes melanistic in specimens 

 as small as 18 mm. In juveniles of the 20- to 25-mm size 

 range, the anterior one-half to two-thirds of the fin is 

 melanistic. In the 25- to 30-mm range, three-fourths or 

 more of the fin is black. In pelagic juveniles larger than 

 this the pigment has spread onto the soft dorsal fin, and 

 covers both the soft dorsal and soft anal fins in benthic 

 juveniles. 



The base of the pectoral fins begins to be covered with 

 melanophores in specimens as small as 14 mm. In 

 specimens as small as 18 mm the melanophores extend 

 onto the basal region of the rays. With further growth the 

 black basal zone enlarges posteriad and becomes a highly 

 characteristic feature of the pelagic juveniles. The pos- 

 terior margin of this zone contrasts sharply with the dis- 

 tal clear region of the fin. In juveniles of the 19- to 25-mm 



size range, the width of the black basal zone averaged 

 20^"? of the fin length. Enlargement of this zone is shown 

 by the average relative widths for successive size ranges 

 (25 to 30 mm, 38^c; 30 to 35 mm, 46%; 35 to 40 mm, 54%; 

 40 to 45 mm, 65%; 45 to 50 mm, 72%; 50 to 55 mm, 76%). 

 Towards the end of the pelagic juvenile stage a pale 

 translucent layer covers the basal region of the pectoral 

 fin and gives the black zone the appearance of a band. 



Distribution. — An extensive discussion of the dis- 

 tribution and abundance of larvae, juveniles, and adults 

 of S. altivelis is given in Moser (1974). 



Sebastolobus alascanus Bean, Figure 26 



Literature. — Larvae, pelagic juveniles, and early 

 demersal juveniles are described in Moser (1974). 



Distinguishing features. — Larvae of Sebastolobus 

 smaller than 10 mm are not separable to species. Dis- 

 tinguishing features ol Sebastolobus larvae up to this size 

 are given in the generic account and in the section de- 

 scribing S. altivelis. Sebastolobus alascanus larvae longer 

 than 10 mm differ from those of S. altivelis in being less 

 robust and in having shorter pectoral fins with a nar- 

 rower base and fewer pectoral rays (Tables 29, 30). These 

 characters carry through into the pelagic juveniles of the 

 two species. The descriptive details for larvae and 

 pelagic juveniles of both species are given in the section 

 on S. altivelis. 



In transforming species of S. alascanus, the first head 

 pigment to appear is a melanistic blotch on the posterior 

 region of the opercle. This gradually spreads anteriorally 

 onto the cheek and in late-stage pelagic juveniles the en- 

 tire head is speckled with melanophores. A blotch begins 

 to form over each side of the gut in larvae as small as 15 

 mm. These enlarge dorsad onto the spinous dorsal fin 

 and posteriad as an irregular mottled sheath that con- 

 trasts markedly with the solidly pigmented sheath of S. 

 altivelis juveniles. In the largest pelagic juveniles the 

 mottling on the dorsal fin and trunk extends posteriad to 

 a vertical from the vent. When the juveniles become ben- 

 thic the mottling spreads onto the remainder of the body 

 and median fins. Melanophores appear on the bases of 

 the pectoral fins in specimens of the 14- to 20-mm size 

 range. A faint band of melanophores appears on the rays 

 in some specimens of this size range but never becomes 

 highly developed and covers only the basal one-third of 

 the fin in the largest pelagic juveniles. 



Distribution.— An extensive discussion of the dis- 

 tribution and abundance of S. alascanus larvae, 

 juveniles, and adults is given in Moser (1974). 



Trachyscorpia Ginsburg 



Literature.— None. 



Distinguishing features. — No larvae are known and 

 the genus is known in the eastern Pacific from one adult 



46 



