EARLY DEVELOPMENT OF THE TEN-POUNDER 



633 



Pigmentation of the 380-mm. adult immediately 

 after death had dorsal surfaces of head and body 

 greenish-black overlaid with silver scales, with 

 the sides shading to silvery below. The dorsal fin, 

 dusky, grading to greenish-black on the anterior 

 edge. The pectoral and pelvic fins, dusky on the 

 anterior portions. The anal, hyaline with a few 

 greenish spots. The caudal fin, dusky to greenish- 

 black, with the ventral lobe darker than the upper 

 (the lowest principal rays are nonpigmented). 

 The eye, greenish-gold and silver with a black 

 pupil. 



OSTEOLOGY 



Several leptocephali and early, mid-, and late 

 metamorphic larvae were stained with alizarine 

 red, using methods described by Hollister (1936) 

 and Evans ( 1948 ) , to study in particular the devel- 

 opment in the caudal fin. 



The fin rays begin to ossify in the following 

 order : caudal, dorsal, and anal rays in the lepto- 

 cephalus period; pectoral rays in the early meta- 

 morphic period ; and pelvic rays in the mid-meta- 

 morphic period. The maxillary and mandible 

 ossify in the leptocephalus period (fig. 18), pre- 

 maxillary in the early metamorphic period (fig. 

 19), and branchiostegals begin to ossify in the 

 mid-metamorphic period (fig. 11). No attempt 

 was made to trace the development of ossification 

 of the various other bones of the head. 



Immediately anterior to and lying against the 

 basal portion of the first pectoral and pelvic ray 

 is a short, slender process which resembles the 

 spinous ray on the paired fins of spiny-rayed fishes 

 (fig. 20). However, its single, flattened base is 

 embedded in the flesh dorsolateral to the insertion 

 of the fins. The ridge on the forward edge of the 

 first ray is replaced by this process (which lies in a 

 depression on the ridge) near the base of the ray. 

 I find no mention of this structure in the literature. 



Caudal development. — The caudal osteology 

 was given special attention when it became ap- 

 parent that the degree of ossification might be of 

 use in separating leptocephali and early metamor- 

 phic larvae of similar size and general appear- 

 ance. Figures 22 to 24 illustrate the degree- of 

 ossification for specimens of similar size but in 

 different stages of development. The density of 

 stippling in the illustrations is to approximate the 

 intensity of the stain. Regan (1910) and Hollister 



h 



I mm. 



Figure 18. — Early metamorphic larva (or leptocephalus), 

 43.3 mm. standard length. Side view of head show- 

 ing ossification as stippled areas (portions which 

 stained with alizarine red). 



Figure 19. — Early metamorphic larva, 26.6 

 mm. standard length. Side view of head 

 showing ossification as stippled areas. 



(1936) presented the caudal osteology of juvenile 

 or adult E. saurus. Figure 21, after Hollister 

 (1936), is of the caudal osteology of a 258-mm. 

 specimen. Nomenclature of caudal bones follows 

 Hollister (1936). 



Figure 22 shows the caudal fin of the 31.3-mm. 

 leptocephalus (fig. 6). Seven hypurals and sev- 

 eral uroneurals are partially ossified. There are 

 1 dorsal and 2 ventral secondary rays ossified in 

 addition to the 19 principal rays. The ventralmost 

 principal ray appears to originate between the two 

 lowermost (anterior) hypurals. 



The complement of rays is the same for the 

 30.9-mm. early metamorphic larva shown in fig- 

 ure 9. However, the illustration of its caudal fin 

 (fig. 23) shows the 5 upper hypurals, 3 of the 4 

 lower hypurals, 1 haemal process, and 2 neural 

 processes as partially ossified. There is no change 

 in the uroneurals. 



Figure 24 shows the caudal fin of the 25.9-mm. 

 late metamorphic larva (fig. 13). Although this 

 specimen is smaller than the other 2 larvae, the 



