118 



BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



KEY TO THE SPECIES 

 FEMALES 



1. Caudal rami twice as long as wide or less; fifth legs 3-segmented 2 



Caudal rami three times as long as wide or more ; fifth legs 



4-segmented 3 



2. First antennae reaching caudal rami ; fifth legs tipped with 2 



setae of equal length ; no spine on outer margin brevicauda (p. 118) 



First antennae only reaching genital segment ; fifth legs tipped 



with 3 unequal setae; a small spine on outer margin lucens (p. 119) 



8, Caudal rami three times as long as wide ; end segment of fifth 

 legs with 2 apical setae, and a third longer one on inner 



margin longa (p. 120) 



Caudal rami five times as long as wide; end segment of fifth 

 legs with 3 subequal apical setae, plumose only proxi- 

 mally princeps (p. 122) 



MALES 



1. First antennae reaching caudal rami or beyond 2 



First antennae not reaching beyond genital segment 3 



2. Grasping antenna on left side; caudal rami twice as long as 



wide or less; left fifth leg much longer than right brevicauda (p. 118) 



Grasping antenna on right side ; caudal rami five times as long 

 as wide, and slightly asymmetrical ; fifth legs equal in 

 length princeps (p. 122) 



3. Caudal rami twice as long as wide ; end segments of fifth legs 



only slightly narrowed distally ; left antenna geniculate lucens (p. 119) 



Caudal rami three times as long as wide ; end segments of fifth 

 legs strongly narrowed distally; right antenna geniculate- longa (p. 120) 



METRIDIA BREVICAUDA Giesbrecht 



Figure 78 



Metridia brevicauda Giesbrecht, Atti Accad. Lincei, Rome, 

 ser. 4, vol. 5, sem. 2, p. 24, 1889 ; Fauna und Flora des 

 Golfes von Neapel, vol. 19, p. 340, pi. 33, 1892. 



Occurrence. — Fifteen males and females taken in 

 surface tow, Station 20115, Granifus; 1 female from 

 trawl wings. Station 2236, Albatross^ off Marthas 

 Vinej^ard. 



Distribution. — Tropical Pacific (Giesbrecht) ; South 

 African seas (Cleve, Stebbing) ; North Atlantic (van 

 Breemen) ; Gulf of Maine (Bigelow). 



Color. — Body transparent and without pigmenta- 

 tion. 



Female. — Metasome twice the length of the uro- 

 some; genital segment somewhat shorter than the 

 Figure i9,.~Metri- abdomen ; caudal rami less than twice as long as 

 a"*FemI^r fl^f t^ii ^^^^'i fi^st antennae reaching the caudal rami; end 

 legs; 6, male, segment of fifth legs with two long, slender apical 

 fifth legs setae equal in length, the two proximal segments un- 



armed; anal segment with a knoblike process at each posterior 

 corner. Total length, 2-2.25 mm. 



