nSHERY BULLETIN: VOL. 77, NO 1 



postflexion specimens (Figure 6E). A few pigment 

 spots dot the anterior margin of the pectoral fin 

 base in postflexion specimens, and extend farther 

 onto the fin base in larger specimens. At dorsal 

 and anal fin formation, pigment clustered in the 

 finfold aligns along the dorsal and anal fin rays, 

 and later in postflexion specimens becomes com- 

 pacted into a narrow band adjacent to the fin 

 bases. Pigment over the pterygiophores, however, 

 is as dense as on the body (Figure 7). 



Morphology . — Larvae of P. coenosus are larger at 

 hatching and at transformation than all other 

 species oi Pleuronichthys except P. decurrens. A 

 3.9-mm NL specimen has much of its yolk sac 

 remaining (Table 7). The smallest specimen in 

 which the left eye begins to migrate is 8.2 mm SL; 

 eye migration is almost complete in our largest 

 transforming specimen, 11.4 mm SL. 



The gut begins to coil and the free section be- 

 comes vertical to the body axis in larvae between 

 5.5 and 6.0 mm NL. Snout-anus distance has a 

 moderate decrease relative to body length in all 

 larval phases and decreases markedly after trans- 

 formation (Table 5). 



As in the other species, relative head length 

 increases during larval development through the 

 postflexion stage, but decreases moderately in 

 juveniles. Both relative snout length and eye size 

 decrease during the three larval phases (Table 5). 



As in other species of Pleuronichthys, body 

 depth increases during each larval stage (Table 5). 

 Relative body depths for larvae of P. coenosus are 

 in the intermediate range compared with other 

 species in the genus. Body depth in juveniles is 

 comparable with that in the relatively deep- 

 bodied P. decurrens. 



Fin and axial skeleton formation. — Fin formation 

 in P. coenosus takes place at smaller sizes than in 

 P. decurrens but at larger sizes than in other 

 species of Pleuronichthys. Larvae undergoing 

 caudal fin formation range from 6.2 to 8.5 mm NL. 

 The smallest fully flexed larva is 7.1 mm SL. The 

 full count of caudal rays is developed on a postflex- 

 ion specimen 8.2 mm SL (Table 8). Dorsal and anal 

 fin formation takes place at the same size as caudal 

 fin formation; rays are mostly formed on late flex- 

 ion specimens and fully formed on the 8.2-mm SL 

 postflexion larva. Pelvic buds are present on all 

 specimens undergoing notochord flexion except 

 the smallest (6.2 mm NL), and the full count of six 

 rays per fin is developed on the 9.6-mm SL post- 

 flexion specimen. Vertebral counts from two 

 cleared and stained larvae, 8.6 and 10.0 mm SL, 

 are 13 + 24. 



Distribution . — Fitch (1963) denoted the distribu- 

 tion of P. coenosus as Alaska to Cape Colnett, Baja 

 California. Collections of our egg and larval mate- 



F|(;i;RE 7. — Transforming specimen of Pleuronichthys roennstis , 10,0 mm. 



118 



