430 BULLETIN" 15 8, UNITED STATES NATIONAL MUSEUM 



Female. — Carapace orbicular, wider than long; second and third 

 segments indistinctly separated dorsally; dorsal plates of second 

 segment large, extending beneath the posterior lobes of the cara- 

 pace, of the third segment with incurved tips, of the fourth segment 

 large enough to cover all the genital segment except its posterior 

 lobes, with smooth margins. Genital segment elliptical, wider than 

 carapace, longer than wide, its posterior lobes turned inward and 

 almost meeting at their tips. Abdomen subquadrangular ; caudal 

 rami large and broad, each armed with a few coarse spines. In the 

 fourth legs each ramus is fused into a single lamina, the endopod 

 unarmed. Total length, 13 mm. 



Male. — Unknown. 



Remarks. — The size of the dorsal plates on the fourth segment will 

 identify this species, which thus far has not been found on any host 

 except the torpedo. 



Genus DINEMATURA Burmeister, 1833 



Female. — Head fused with first segment, second, third, and fourth 

 segments free, each with a pair of dorsal plates; fifth and genital 

 segments fused with a pair of dorsal plates; a sixth segment dis- 

 tinctly separated from the genital segment in front of the abdomen, 

 with a pair of dorsal plates and rudimentary legs. Abdomen 1- 

 segmented, attached to the posterior end of this sixth seg-ment. First 

 four pairs of legs biramose, rami of first legs 2-segmented, of second 

 and third legs 3-segmented, of fourth pair 1-segmented. 



Male. — Carapace like that of female; dorsal plates of second seg- 

 ment lateral and small ; no plates on third segment ; those on fourth 

 segment rudimentary; genital segment oblong, widest posteriorly; no 

 sixth segment; no leg rudiments. Abdomen 2-segmented, segments 

 subequal; caudal rami large, foliaceous, and armed with plumose 

 setae. Both rami of fourth legs distinctly 2-segmented and armed 

 with spines only. 



KEY TO THE SPECIES 



1. Carapace one-third entire length ; dorsal plates of fourth segment 



much longer than wide, with rounded tips producta (p. 431) 



Carapace one-half entire length ; dorsal plates of fourth segment 



much wider than long, with concave posterior margin latifolia (p. 432) 



1. Second and fourth segments without dorsal plates ; distal abdom- 

 inal segment longer than wide producta (p. 431) 



Second and fourth segments with small dorsal plates; distal ab- 

 dominal segment wider than long latifolia (p. 432) 



