435 



part of the leg is shorter than the 2nd segment and tucked under it; the 

 5th segment is the longest of the distal segments, the 7th segment is 

 shortest, bud-shaped, with small spines at the end. 



The urosome is shorter than the last two somites of the pleon; more- 

 over, the last (geminate) urosomite is almost half the length of the first. 

 The telson is roundish or roundish-triangular, its width at the base almost 

 equal to the length of the distal margin of the last urosomite. 



Distribution: Widely distributed in the tropical, subtropical, and tem- 

 perate waters of the World Ocean. It often forms local swarms near the 

 surface. It lives in the surface zone and performs diurnal vertical migra- 

 tions, rising to the surface at night (Thurston, 1976b). 



353 3. Genus Primno Guerin-Meneville, 1836 



Guerin-Meneville, 1836: 2; Stebbing, 1904: 38; Bowman and Gruner, 

 1973: 40; Bowman, 1978: 2.—Euprimno Bovallius, 1889: 397; 

 Stephensen, 1924: 143; Pirlot, 1929: 129. 



The head has a small rostrum. Antennae I in females are slightly 

 longer than the head and three-segmented. Antennae II are rudimentary. 

 In males both antennae have a long, multisegmented flagellum. 



Somites! and II of the pereon are free. All the pereopods except for 

 pair V are simple, the 2nd segment of pereopods I has a well-developed 

 gland, the duct passing through all the segments and opening at the 

 tip of the claw. Pereopods V have a powerful subchela; the 5th seg- 

 ment is broadened and has a complex denticulation all along the entire 

 anterior margin; the 6th Segment is shorter than the 5th and may be 

 completely clung close to the anterior margin of the 5th segment. Pere- 

 opods VII are completely segmented, the last segment having an obtuse 

 apex. Somite VII of the pereon and the first two somites of the pleon 

 bear medium-sized, backwardly directed dorsal teeth. 



The pleon is massive and higher than the pereon. The posterior distal 

 angle of the epimeral plates is stretched posteriorly and in somite III is 

 very acute. None of the urosomites are longer than somite III of the 

 pleon. The basipodite of all the uropods is broadened, with an acute end, 

 and its margins sometimes denticulate. The telson is small, roundish- 

 triangular, and much narrower at the base than the last urosomite. 



Type species: Primno macropa Guerin-Meneville, 1836. 



Notes: Until recently the genus Primno was considered monotypic. 

 In 1978, Bowman published a revision of the genus, substantiating, 

 his assumption that P. macropa is, in reality, a species aggregate. He 

 described two new species — P. brevidens and P. johnsoni — and restored 

 the independent status of the species P. latreillei Stebbing, which 

 together with the type species, P. macropa Guerin-Meneville, constitute 

 the new content of the genus Primno as proposed by Bowman. It must 



