present. Four species of chaetognaths, P. 

 draco, S. hexaptera, S. serratodentata, and S. 

 bipanctata and 1 species of pteropod, Creseis 

 acicula, were classed as abundant. Two species 

 of chaetognaths, S. lyra and Eukrohnia subtilis, 

 and 7 species of pteropods, Limacir.? inflata, 

 L. trochiformis, L. lesueuri, Creseis viigula. 



Cavolinia inflexa, Styliola subula, and Diacria 

 quadridentata were classed as comnaon. 



The northern limits of the zone were drawn 

 where P. draco ceased to be a common constit- 

 uent of the plankton (table 4, fig. 2). P^. draco 

 was selected as the best indicator of this zone 



45° 



40° 



35' 



30° 



25° 



LiJ 



a 



35° 



30° 



o 



25° 



40° 



35 = 



30° 



25' 



I70°E 



180° 



I70°W 

 LONGITUDE 



160° 



150° 



140° 



Figure 2. -- Seasonal variation in the northern limits of the Subtropic Zone 

 (dashed line) as defined by the abundance of Pterosagitta draco . The 

 symbols indicate the relative abundance of this species at each station 

 where it occurred in the plankton collections. 



