325 



^Pi-ia ^ 



Fig. 130. Hyperia galba (Montagu) (after Bowman, 1973). 



The 6th segment of pereopods I and II bears many strong setae on 

 the lateral surface; this ornamentation is especially well developed in 

 large specimens. In f. medusarum the setae extend to the apical end of 

 the claw while in f. hystrix they are relatively shorter and the claw is 

 longer. The posterior margin of the 6th and 7th segments is denticulate; 

 this denticulation, however, is not readily discernible in f. medusarum 

 because masked by the setae and unevenness of the posterior margin. 

 The distal part of the 4th and 5th segments of pereopods III-IV bears a 

 row of long and short spines, the long spines extending to half the width 

 of the segment; in males these spines are fewer and may even be totally 

 absent on the 4th segment; the 6th segment is finely denticulate, the 

 anterior margin generally not armed, but sometimes bears a few spinules. 

 Pereopods V-VII are approximately equal in length in females but in 

 males pereopods V are somewhat longer than the identical pereopods VI 

 and VII. The lower posterior angles of the epimerons are produced into 

 denticles, especially well developed in epimeron III. 



Notes: Populations from different regions of the area of distribution 

 exhibit small morphological differences. Individuals from the Polar 

 Basin, Bering Sea, and the Pacific Ocean coast of Canada (typical 

 H. medusarum) are much larger, with much longer setae on pereopods I 

 and II. Populations from the southern part of the area of distribution (for 

 example, coastal areas between San Diego and Vancouver and off Japan) 



