570 BULLETIN 159, UNITED STATES NATIONAL MUSEUM 



78. First legs natatory, with setae, endopod segments in male at 



right angles to each other; segments of fifth legs fused into a 



broad lamina; pelagic, surface tow cf 9 Euterpina Norman, 1903 



First legs prehensile, one or both rami armed with claws; fifth 



legs of usual pattern, with 2 distinct segments 79 



79. Exopod of first legs shorter than endopod, rarely 1-segmented 80 



Exopod of first legs longer than endopod, always 2-segmented 81 



80. Exopod of second antenna 2-segmented; exopod of first legs 



2-segmented; basal expansion of fifth legs as long as end seg- 

 ment, with spinelike setae; littoral, tide pools. 



cT 9 Pseudothalestris Brady, 1883 (p. 210) 

 Exopod of second antenna 3-segmented; exopod of first legs 

 1-segmented; end segment of fifth legs longer than basal 

 expansion, with plumose setae; littoral, shallow water. 



c?" 9 Parawestwoodia Sharpe, 1910 



81. Body strongly depressed, most segments with lateral lamellae 82 



Body cylindrical, without lamellae; metasome passing insensi- 

 bly into urosome; spines on second antennae and legs not 

 pectinated (Antarctic Ocean) 9 Perissocope Brady, 1910 



82. Fifth segment abruptly narrowed, without lateral plates; 



spines on second antennae and legs pectinated; exopod of 

 second antenna 2-segmented, 6 setae; littoral, in algae. 



d^ 9 Zaus Goodsir, 1845 (p. 190) 

 Fifth segment as wide as fourth, with lateral plates; spines on 

 second antennae and legs not pectinated; exopod of second 

 antenna 1-segmented, with 2 setae; beach sands. 



cf 9 Zausodes, new genus (p. 187) 



83. One or both rami of first legs conspicuously broadened or mod- 



ified 84 



Neither ramus of first legs much broadened or specially modified 96 



84. Fifth legs composed of a single segment 85 



Fifth legs of the usual form, 2 distinct segments 88 



85. Endopod of first legs broadened, exopod normal, both natatory; 



central body segments produced laterally into long sickle- 

 shaped lamellae; possibl}' parasitic. 



9 Megarthrum Norman and Scott, 1906 

 First legs only slightly broadened, but considerably modified 



for prehension ; central body segments without lateral lamellae 86 



86. Body much swollen anteriorly, narrowed posteriorly; first 



antennae 5- or 6-segmented, with process on second segment; 



exopod of second antenna lacking 87 



Body elongate, nearly the same diameter throughout; first 

 antennae 8-segmented, no process on second segment; exopod 

 of second antenna 1-segmented, 3 setae; parasitic on land 

 crabs cf Cancrincola Wilson, 1913 



87. Second antennae straight, not enlarged at tip; segments of fifth 



legs fully fused, end segment with 4, basal segment with 3, 



plumose setae; in a holothurian 9 Abacola C. L. Edwards, 1891 



End segment of second antenna turned at right angles and 

 enlarged at tip; segments of fifth legs fused, each with 1 or 2 

 small spinules; littoral, among algae. cT 9 Metis Philippi, 1843 (p. 305) 



