68 BULLETIN" 15 8, UNITED STATES NATIONAL MUSEUM 



ReTTMrhs. — This species has never before been reported from the 

 American side of the Atlantic, but seems quite common in European 

 waters. It may be distinguished by the unequal notching of the 

 genital protuberance in the female and by the structure of the chela 

 on the left fifth leg in the male. 



Family PHAENNIDAE 



Genus XANTHOCALANUS Giesbrecht, 1892 



Metasome ellipsoidal, head separated from the first segment ; fourth 

 and fifth segments fused and produced at the posterior corners into 

 acute lappets; exopods of first four pairs of legs 3-segmented; 

 endopod of first legs 1-segmented, of second legs 2-segmented, of 

 third and fourth legs 3-segmented ; fifth legs uniramose, symmetrical 

 in female, asymmetrical in male, the right leg rudimentary or even 

 lacking. 



KEY TO THE SPECIES 



FBMALES 



1. Each fifth leg with only 3 spines at tip, 1 terminal, and 1 on 



each lateral margin 2 



Each fifth leg with 4 spines at tip, arranged sometimes sym- 

 metrically, sometimes asymmetrically 3 



2. All 3 spines equal in size ; inner margins of 2 basal segments 



with a few small spines greenii (p. 68) 



Terminal spine considerably larger than other two ; no spines on 

 inner margins of basal segments subagilis (p. 70) 



3. The largest of the 4 spines terminal, other 3 much smaller, all on 



outer margin propinquus (p. 73) 



Two of the spines terminal and unequal in size, the other two 

 lateral, one on each side 4 



4. Terminal segment one-half longer than wide; 2 basal segments 



with spines on their inner margins borealis (p. 70) 



Terminal segment twice as long as wide ; inner margin of second 



segment smooth, of third segment with short hairs pinguis (p. 71) 



MALES 



1. Fifth legs about equal in length ; right leg 4-segniented, left leg 



5-segmented, end segment needle-shaped subagilis (p, 70) 



Left fifth leg much longer than right 2 



2. Right fifth leg 6-segmented, almost reaching the center of 



fourth segment of left leg pinguis (p. 71) 



Right fifth leg 4-segmented and much shorter 3 



3. Right fifth leg only reaching middle of first segment of left leg, 



its 3 distal segments as wide as long propinquus (p. 73) 



Right fifth leg reaching distal end of second segment of left leg, 

 its 3 distal segments much longer than wide borealis (p, 70) 



XANTHOCALANUS GREENII Farran 



FiGUBB 45 



Xanthocalanus greenii Fabban, Rep. British Assoc. Adv. Sci. for 1904, p. 603, 

 1905. — VAN Bkeemen, Nordisches Plankton, Zoologiseher Teil, vol. 4, Ento- 

 mostraca, Copepoden, p. 60, fig. 67, 1908. 



