FISHERY BULLETIN: VOL. 71, NO. 3 



stages. Most bones of the neurocranium cannot 

 be distinguished in stained larvae. 



Terminology is based on Gregory (1933), 

 Lagler, Bardach, and Miller (1962), Fraser 

 (1968), and Wolcott, Beirne, and Hall (1968). 



Fin Formation 



A large finfold surrounds the body of early 

 stage larvae from the head, around the tail tip, 

 to the anus. The first fins to form are larval 

 pectorals. Fin rays begin to ossify in larvae of 

 5-6 mm in dorsal, anal, caudal, and pelvic fins 

 in both species (Table 6). Fin rays do not 

 appear in the pectoral fins until metamorphosis. 

 Fin formation in both species is completed in 

 the following order: caudal, dorsal and anal, 

 pelvic, and pectoral. 



Incipient caudal fin rays become visible in 

 the posteroventral region of the finfold as early 

 as 4 mm in E. microstomus. Fin rays ossify 

 after the urostyle begins to turn dorsad at about 

 5 mm in both species. The first rays to take up 

 alizarin stain are in the center of the fin. 

 Development proceeds dorsally and ventrally 

 until the full complement of 17 caudal fin rays 

 is attained by 7 mm in E. microstomus and 9 

 mm in C. arctifro)is. 



The proximal portions of incipient dorsal fin 

 rays may appear in the center of the dorsal 

 finfold as early as 4 mm in E. microstomus. 

 Ossification of rays in the dorsal fin begins 

 centrally at about 5 mm and proceeds anter- 

 iorly and posteriorly. The full complement is 

 achieved by 8 mm. In C. arctifrons, a notch 

 appears dorsally in the anterior portion of the 

 finfold at about 4 mm. By 5 mm, three elon- 

 gated fin rays become ossified in this region. 

 These rays persist until the onset of metamor- 

 phosis, although they appear to get propor- 

 tionately shorter with increasing age. Forma- 

 tion of the rest of the dorsal fin is smilar to that 

 of E. microstomus. Ossification of fin rays be- 

 gins centrally at about 6 mm and proceeds 

 anteriorly and posteriorly. The full complement 

 is attained by 10 mm. During dorsal fin for- 

 mation in C. airtifyoiis, one fin ray appears an- 

 terior to the three elongated rays, which then 

 become the 2d, 3d, and 4th rays. The 1st ray 

 is inconspicuous and is best seen on the blind 

 side. Only its base takes up alizarin stain until 

 the three elongated anterior rays become re- 

 duced in size. With development, the dorsal 

 fin moves progressively anteriorad in both 

 species. As the right eye moves over the ridge 



Table 6. — Ranges of meristic counts in early stages of Etropiis microstomus and Citharichlhys arctifrons. 



' Larval bud. 



2 Size range in which final or adult count is consistently achieved. 



752 



