rowing may indicate a functional role of the deep, 

 narrow form of the ventral part of the body in 

 burrowing. 



Larval Development 



Morphometric and meristic features of an ex- 

 cised embryo ( 2 wk prior to hatching) and larvae of 

 nine posthatching ages are presented in Table 1. 

 The outstanding feature of the late embryo was 

 the presence of caudal fin rays and a flexing 

 notocord with the posterior margins of the hypural 

 plates about 45° to the horizontal body axis. This 

 precocious development of the caudal fin remained 

 a diagnostic character throughout the larval 

 period and probably contributed to the rapid 

 swimming speeds discussed earlier. 



The late embryo and the newly hatched larvae 

 have a large oil droplet positioned anteriorly in the 

 yolk. The abdomen has about 40 melanophores 

 radiating from the dorsal gut surface. In addition 

 to the features detailed in Table 1, these early ages 

 have a few external melanophores in the nasal 

 region, lower jaw angle, cranial region (7-10), and 

 anterior mandibles (Figure 1). There is also an 

 internal melanophore anterior to each otic capsule 

 and, in fresh material, about 30 xanthophores over 

 the cranium. Three preopercular spines are pres- 

 ent as are the pectoral fin rays. 



By 9 d hatching age, the posterior margins of the 

 hypural plates are approaching a vertical orien- 

 tation and have an increased number of 

 melanophores, while the caudal and pectoral fin 

 rays have increased in length. There is a row of 4 or 

 5 small melanophores along each side of the an- 

 terior insertion of the dorsal fin fold and an inter- 

 nal row of about 24 melanophores along the 

 notocord (less clearly visible than external pig- 

 ment, therefore not illustrated). Eight small 

 melanophores have appeared in the cranial re- 

 gion, clustered among six larger ones, previously 

 developed. A single melanophore has appeared on 

 the ventral midline of the lower jaw (not visible in 

 side view). Rows of melanophores have also ap- 

 peared along the anterior end of the mandibles 

 and horizontally on the dorsal portion of the oper- 

 culum. Snout melanophores become prominent by 

 this stage, as do teeth on the lower jaw. These teeth 

 are easily visible at this stage, becoming progres- 

 sively reduced until, at 25 d hatching age, they are 

 no longer noticeable. 



The 18 -d specimen has vertical posterior mar- 

 gins on the hypural plates, a forked caudal fin, and 



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