COPEPODS OF THE WOODS HOLE KEGION 



85 



developed in the left leg, the spines on the right leg reduced to a 

 single one on the inner margin of the end segment. Total length, 

 2.3-2.5 mm. 



Male. — Young only known ; fifth legs uniramose, 3-segmented. 



ReTnarks. — This species is also pelagic and frequents the open 

 ocean far from shore; it may be recognized by the structure of the 

 fifth legs and the short urosome. 



Family CENTROPAGIDAE 

 Genus CENTROPAGES Kr0yer, 1849 



Head narrowed anteriorly, with a distinct cervical depression on 

 the dorsal surface; fifth segment separated from the fourth, its 

 posterior corners rounded or 

 pointed ; urosome somewhat 

 asymmetncal in the female, 

 3-segmented, symmetrical in 

 the male, 4-segmented ; first an- 

 tennae reaching to or beyond 

 the caudal rami, the right one 

 transformed in the male; rami 

 of the first four pairs of legs 

 and of the fifth pair in the 

 female 3-segmented; endopods 

 of fifth legs in male 3-seg- 

 mented, right exopod 3-seg- 

 mented, the two end segments 

 forming a strong chela, left 

 exopod 2-segmented. 



Figure 58. — Scoledthricella ovata: a. Female, 

 dorsal ; b, female, fifth leg 



KETT TO THE SPECIES 



1. Posterior corners of fifth segment rounded; urosome symmetri- 



cal bradyi (p. 86) 



Posterior corners of fifth segment with sharp spines; uro- 

 some more or less asymmetrical 2 



2. First antennae reaching about 2 segments beyond tips of caudal 



rami; genital segment with several stiff spines typicus (p. 87) 



First antennae reaching base of caudal rami; genital segment 

 with a single recurved spine on ventral surface hamatus (p. 89) 



MALES 



1. Posterior corners of fifth segment rounded; thumb of chela on 



right fifth leg laminate and bluntly rounded bradyi (p. 86) 



Posterior corners of fifth segment with sharp spines ; both rami 



of chela on right fifth leg acuminate 2 



2. First antennae with toothlike processes on some of the basal 



segments; fifth leg chela stout, overlapping caudal rami— typicus (p. 87) 

 First antennae without toothlike processes; fifth leg chela 



slender, scarcely reaching anal segment hamatus (p. 89) 



