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PROCEEDINGS OF THE NATIONAL MUSEUM 



Figure 9. — Distribution of Parathemisto pacifica Stebbing. Solid circles, positive sta- 

 tions; open circles, negative stations. CCOFI area outlined by dashed line. Approx- 

 imate southern limit of distribution shown by hachured line. 



Pacific gives us a boundary line in the north central Pacific between 

 latitudes 42° and 43° N. On the basis of an analysis of the distribu- 

 tion of chaetognaths and pteropods in about the same region (22°-50° 

 N., 170° E.-145° W.), Hida (1957) established the Subarctic Zone, 

 the southern limit of which was defined by the occurrence in abun- 

 dance of the chaetognaths Sagitta elegans and Eukrohnia hamata. 

 Hida found this boundary to lie between 43° and 45° N.; this finding 

 agrees reasonably well with my suggested boundary for Parathemisto 

 pacifica. It has already been mentioned that Bogorov and Vino- 

 gradov (1955) cited P. japonica as well as the above-mentioned 

 chaetognaths as characteristic species of a faunal zone corresponding 

 to Hida's Subarctic Zone. In Brodsky's (1955b) scheme for dividing 

 the north Pacific into zoogeographical provinces according to the 

 copepod faunas, P. pacifica fits roughly into his epipelagic temperate 

 province. However, P. pacifica extends somewhat farther south and 

 not so far to the north, for Brodsky's temperate province includes the 

 southern part of the Chukchi Sea. 



The northern limits of the area inhabitated by P. pacifica are not 

 known in detail. The species has not been reported from the Arctic 

 Ocean, and I have not found it in any of the plankton samples which 

 I have examined from the Beaufort and Chukchi Seas. Three investi- 

 gators have reported it from the Bering Sea as P. japonica (Behning, 

 1939; Bulycheva, 1955, Vinogradov, 1956). Further collections in the 



