436 



be pointed out immediately that P. johnsoni is similar to P. latreillei in 

 all features except for the larger size attained by sexually mature females 

 (9 mm and 6.5 mm respectively). Furthermore, his illustrations depict no 

 significant differences between these species. Nor does Bowman provide 

 a description of P. johnsoni, confining himself to a brief note about 

 the similarity of the two. Hence we cannot consider P. johnsoni an 

 independent species and relegate it to a synonym of P. latreillei. 



The species P. brevidens has several characteristic features differen- 

 tiating it from the other species of the genus. In distribution, it is partially 

 sympatric with P. macropa in the northeastern part of the Pacific Ocean, 

 while in warmer water regions it is sympatric with P. latreillei. Such a 

 distributional pattern also supports its species independence. 



KEY TO SPECIES OF GENUS PRIMNO 

 (after Bowman, 1978, with alterations) 



1. Large denticles on anterior margin of 5th segment of pereopods V 

 equal in length to 1/3 width of segment 2. P. brevidens Bowm. 



— Large denticles on anterior margin of 5th segment of pereopods V 

 almost equal in length to total width of segment 2. 



2. In pereopods V denticulation of proximal part of anterior margin of 



5th segment begins with group of small denticles 



I. P. macropa Guerin-M6n. 



— In pereopods V denticulation of proximal part of anterior margin of 

 5th segment begins with much larger denticle, followed by group of 

 smaller ones 3. P. latreillei Stebb. 



354 1. Primno macropa Guerin-Meneville, 1836 (Fig. 189) 



Guerin-Meneville, 1836: 4; BovaUius, 1887a: 28; Barnard, 1930: 

 424; 1932: 287 (part.); Thorsteinson, 1941: 93; Hurley, 1955: 172; Vino- 

 gradov, 1956: 209; 1962: 22; Bowman, 1978: 3. — menevillei Stebbing, 

 1888: 1441 .-Antarctica Stebbing, 1888: 1448. 



Length up to 21 mm. 



The body is laterally compressed. The rostrum (top view) is bluntly 

 truncate. The pereon is approximately 3.3 times as long as the head 

 and slightly longer than the pleon. The median dorsal teeth are coarser 

 and longer than in other species of the genus, the same is true of the 

 posterior denticle on epimeral plate III. The oral sinus occupies nearly 

 2/3 the height of the head. 



The length of the 2nd segment of pereopods V is approximately 

 three times its width; the 5th segment is slightly longer than the 2nd; the 

 proximal denticles on the anterior margin are small, the larger denticles 

 on the anterior margin are slightly shorter than the width of the seg- 

 ment, the smaller denticles approximately the same length as the width 



