COPEPODS OP THE WOODS HOLE KEGION 461 



NEMESIS LAMNA Risso. 1826 



Plate 32 



Nemesis lamna Risso, Histoire naturelle des principales productions de TBurope 



Meridionale, vol. 5, p. 135, pi. 5, fig. 25, 1826. 

 Nemesis mediterranea Helleb, Reise der Osterreichischen Fregatte Novura, 



vol. 2, pt. 3, Crustacea, p. 220, pi. 21, 1865. 



Occy/rrence. — Both sexes were obtained from the gills of the great 

 white shark {Carcharodon carcharias) in August, 1916, and again 

 from the same host in July, 1924, both sharks caught in the fish nets 

 on Marthas Vineyard. 



Distribution. — Mediterranean (Risso, Milne Edwards, Brian, 

 Valle) ; European seas (Roux, Guerin) ; California coast on gills of 

 mackerel shark {Iswus punctatus) (Wilson). 



Color. — Body a light tan, the dorsal surface of the carapace and 

 the centers of the second, third, and fourth segments in the female a 

 light brown ; spermatophores d^rk reddish brown, almost black ; egg 

 strings dark brown. 



Female. — Cephalothorax obovate, frontal margin straight, posterior 

 portion overlapping the second segment considerably narrowed. The 

 dorsal carapace does not reach the posterior margin, but leaves a 

 narrow free border around the posterior end. Second, third, and 

 fourth segments about the same length and wider than the carapace, 

 with deep lateral sinuses between them. Each of these segments 

 carries on its dorsal surface a pair of plates, which are so completely 

 fused as to appear single, are inlaid into the dorsal surface, and 

 cover only the center of the segment, leaving a wide naked border 

 around the lateral and posterior margins. The lateral sinuses be- 

 tween the fourth and fifth segments are deeper than the two pairs 

 that precede them, and their inner ends are curved backward into 

 the anterior margin of the fifth segment. The latter is fully as long 

 as the fourth segment and scarcely narrower, and carries on its 

 rounded posterior corners the rudiments of the fifth legs. The genital 

 segment is about one-third the width of the fifth segment, with 

 strongly convex lateral margins. Abdomen half as wide as the geni- 

 tal segment, 2-segmented, the anal segment twice as long as the basal. 

 Egg strings narrow, but three times as long as the body ; spermato- 

 phores ovoid, the two fully as large as the genital segment and 

 extending out at right angles to the body axis. 



First antennae filiform, 12 to 15 segments, the basal segment con- 

 siderably wider and longer than any of the others. Second antennae 

 longer than the first pair, 3-segmented with a terminal claw, which 

 is strongly curved and bears on its inner margin near the base a 

 short bipartite spine; the second segment also carries a small spine 

 on its inner margin. Second maxilla 2-segmented, the segments about 

 71937— S2 31 



