388 BULLETIN" 15 8, UNITED STATES JSTATIONAL MUSEUM 



nae 3-segmented, prehensile; rami of first four pairs of legs 3-seg- 

 mented, the two terminal segments of the third endopod sometimes 

 fused; fifth legs uniramose, 2-segmented. 



KEY TO THE SPECIES (FEMALES) 



1. Urosome nearly in line with metasome ; second antenna wide 

 and flattened, its second segment as wide as long. 



laticornis, new species (p. 388) 

 Urosome at right angles to metasome ; second antenna narrow 



and cylindrical, its second segment twice as long as wide — pulex (p. 389) 



DOROPYGUS LATICORNIS. new species 



Plates 1, c; 24 



Occwnfence. — Both sexes were taken from the branchial cavity of 

 Molgula manhattensls at Woods Hole, July, 1924. One of the fe- 

 males is made the holotype of the new species with U.S.N.M. No. 

 56570; the other females and a male become paratypes, with U.S.N.M. 

 No. 56571. 



Color. — Body yellowish white, the ova in the incubatory pouch dark 

 yellow; eye dark ruby-red. 



Female. — Head turned downward, the sides of the carapace over- 

 lapping the first segment and reaching the second segment ; the first 

 thoracic segment the shortest, the second and third segments increas- 

 ing in length; the incubatory pouch not much inflated dorsally and 

 broadly rounded posteriorly, produced backward on the dorsal sur- 

 face of the genital segment beyond the center of the latter; eggs 

 rather large and few in number. Urosome slender, 4-segmented, the 

 genital segment longer than any of the abdominal segments, but no 

 wider ; the three abdominal segments about the same length, but ta- 

 pered in width; anal segment notched at the center of its posterior 

 margin. Caudal rami slender, nearly twice the length of the anal 

 segment, five times as long as their basal width, each with two minute 

 spines at its tip, the lateral margins smooth. 



First antennae 9-segmented, the two basal segments twice as wide 

 as long, the next four segments tapering regularly, the last three seg- 

 ments about the same width, all except the first basal segment heavily 

 armed with setae. Second antennae much widened and flattened, 

 the basal segment enlarged at its distal end, with a rounded knob 

 bearing a short spine on the inner corner. The second segment is a 

 little wider than long, the inner margin strongly convex at the proxi- 

 mal end. Between this convexity and the one on the distal end of 

 the basal segment is a deep triangular notch, which stands out con- 

 spicuously when examining the antenna. The end segment is two 

 and a half times as long as wide and is tipped with a stout curved 

 claw and a seta. 



