thetic mounting medium Covermount, and viewed 

 under a compound light microscope with bright field 

 illumination at 100X and 400X magnification. A 

 radial measurement from the primordium to the ros- 

 trum margin was taken on the right sagitta of each 

 fish, to the nearest 0.01 mm. 



The sagittae were thin enough that growth rings 

 could be read with no further preparation. Five 

 counts were made using both the right and left sagit- 

 tae at400X and repeat counts were made at 100X. A 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



plot of fish standard length against the number of 

 sagittal rings (TV) was drawn, and from this an average 

 growth rate was calculated. 



Results and Discussion 



The sagittae of C. hippurus are extremely small (2.6 

 mm in a fish of 1,100 mm SL). The rostrum is 

 exaggerated and separated from the antirostrum by a 

 deep V-shaped excisural notch (Fig. 1). Rings are 

 clearly visible on the lateral or convex surface of the 

 sagittae from the primordium to the margin (Fig. 2). 

 These could be counted accurately on all specimens 



FIGURE 2.— Lateral surface of 

 sagitta of Coryphaena hippurus 

 showing 51 increments from the 

 primordium to the margin. P = 

 primordium, I = increments, M 

 = margin. 



907 



