ART. 5. NORTH AMERICAN PARASITIC COPEPODS WILSON. 59 



length beyond the carapace, and ending in a powerful sickle-shaped 

 claw. First four pairs of legs biramose, rami two-jointed; fifth legs 

 rudimentary, uniramose, two- jointed. Egg strings as long as the 

 body, eggs thick and but little flattened. 



Generic characters of male. — Body narrow and elongate. First 

 thorax segment partially separated from the head ; second, third, and 

 fourth segments increasing in size ; fifth segment smaller ; genital seg- 

 ment smaller than the fifth segment; abdomen two-jointed; anal 

 laminae narrow, elongate. 



Basal joints of first antennae enlarged; second antennae small and 

 weak. Maxillipeds modified into huge chelae, the dorsal jaw stout 

 and bluntly rounded at the tip, the ventral jaw a long pointed claw. 

 Fifth legs relatively much larger than in the female. 



Type of the germs. — Nemesis Jamna Risso, monotypic. 



KEY TO THE SPECIES. 



1. Cephalothorax triangular, widest at posterior margin, pointed anteriorly ; 



first antennae six-jointed carcJiariae-glauci (Hesse), 1883, p. 60 



1. Cephalothorax ovate, widest at anterior margin ; fifth thorax segment as wide 



as the three preceding it larnna Risso, 1826 



1. Cephalothorax ovate or elliptical, widest through the center ; fifth segment 



half the width of the fourth or less ; first antennae twelve- to fourteen- 

 jointed 2 



2. Cephalothorax nearly as wide as the second segment and smoothly rounded ; 



posterior margin of fifth segment three-lobed ; fifth legs one-jointed, without 

 setae atlantica, new species, p. 60 



2. Cephalothorax two-thirds as wide as the second segment, with a knob on each 

 lateral margin in front of the center ; posterior margin of fifth segment 

 evenly rounded; fifth legs two-jointed versicolor Wilson, 1913 



2. Cephalothorax less than half the width of the second segment, smoothly 

 rounded ; fifth segment also smoothly rounded ; fifth legs one-jointed, with 

 setae robvsta (P. J. van Beneden), 1853 



Remarks. — This genus was established in 1826 by Risso with the 

 species N. lamna. Two years later Roux accepted Risso's name for 

 some specimens which he had obtained from Lamna cornuhica Lin- 

 naeus. But he tried to establish a new species, to which he gave the 

 name carchariarium., upon other specimens taken from the gills of 

 Carcharias vulpes Cuvier. In 1865 Heller, after examining Roux's 

 type specimens in the Vienna Museum, concluded that the two species 

 lamina and carchaHamm were simply different development stages of 

 the same copepod, but instead of giving Risso's name priority and 

 making Roux's name a synonym he discarded both names and called 

 the species N . mediterranea. This name accordingly becomes a second 

 synonym of lamna, as indicated by Brian in 1906, although it had 

 previously been adopted by Richiardi, Valle, Bassett- Smith, and even 

 by Brian himself in 1898.28 



»* Atti. Soc. Ligustica Sci. Nat. e Georg., vol. 9, p. lo. 



