150 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



and pterotic and main preopercular spines remain 

 distinct.) The dermal spines are long, slender, 

 with a gradual taper, and arise from the centers of 

 irregularly shaped (though generally rounded) 

 plates which appear slightly superior to connective 

 tissues. The plates (or bases) have 3 or 4 con- 

 centric raised ridges connected at random by 

 numerous raised radials. The concentric ridges 

 make a continuous spiral on some plates, but on 

 others are entirely separate ridges (fig. 19). 



FiCiURE 19. — Sailfish larva, 101 millimeters long (USNM 

 107200): Above, dorsal view of dermal scale; below, 

 oblique view. Diameter of scale approximately 0.6 mil- 

 limeter. 



SAILFISH JUVENILE, 374 MILLIMETERS 



(Fig. 20) 



Observations are from a mounted specimen, 

 and only those that appear accurate are presented 

 (the first dorsal fin and the pelvic fins are artificial). 

 There is no evidence of spines or serrated keels on 

 the head. The only evidence of teeth are minute 

 spines present mainly on the ventral surface of 

 the snout in the portion extending beyond the tip 

 of the mandible. Tlie caudal fin lobes are long 

 and falcate, and the anal fin is separated. 



GROWTH AND DEVELOPMENT 



CHANGES IN RATES OF GROWTH OF VARIOUS 

 BODY PARTS 



Several of the numerous measurements and 

 meristic counts taken from the 168 specimens 

 examined were selected to portray changes in rates 

 of growth of various body parts. Original meas- 

 urements were used in establishing the curves 

 appearing in figures 26 to 35. As the graphs are 

 largely self-explanatory, only the salient points are 

 summarized. The curves are drawn to include all 

 specimens less than 10 mm. in standard length, but 

 only the Atlantic sailfish beyond 10 mm. It was 

 considered that insufficient data were available to 

 fit curves for the unidentified species. The fol- 

 lowing comments apply only to the Atlantic 

 sailfish. 



The rate of increase in head length approximates 

 that of the standard length, with indications of a 

 slightly higher rate in specimens smaller than 

 10 mm. (fig. 26). 



The rate of increase in head width approximates 

 that of the standard length in specimens smaller 

 than 10 mm. and falls well below it in specimens 

 between 10 and 100 mm. (The high value for the 

 101-mm. specimen has been disregarded in 

 drawing the curve, fig. 27.) 



The rate of increase in head depth approximates 

 that of the standard length in specimens smaller 

 than 10 mm., decreases and falls below it in 

 specimens between 10 and 40 mm., and increases 

 to approximate it in specimens exceeding 40 mm. 

 (fig. 28). 



The rate of increase in snout length exceeds, 

 considerably, that of the standard length in 

 specimens smaller than 10 mm., decreases some- 

 what (but still exceeds the standard length rate) 

 in specimens between 10 and 100 mm., and falls 

 slightly below it in specimens exceeding 100 mm. 

 (fig. 29). 



The rate of increase in lower jaw length exceeds 

 that of the standard length in specimens smaller 

 than 10 mm., decreases and falls below it in 

 specimens between 10 and 100 mm., and increases 

 to approximate it in specimens exceeding 100 mm. 

 (fig. 30). 



