176 



BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



the form of the fifth legs, and is evidently a bottom species, living in 

 the sand at moderate depths. 



Genus MICROSETELLA Brady and Robertson, 1873 



Body slender and compressed laterally; urosome as wide as 

 metasome; head fused with first segment; urosome 4-segmented 

 in female, apj)arently 6-segmented in male, the genital segment 

 being completely divided. First antennae slender, elongate, geni- 

 culate in male, with two elongate aesthetasks; exopod of second 

 antennae 3-segmented; first four pairs of legs with 3-segmented 

 rami; fifth legs 2-segmented, distal segment imperfectly trilobate, 

 with 3 setae, inner expansion of basal segment with 2 setae. 



KEY TO THE SPECIES (BOTH SEXES) 



1. Caudal setae shorter than body ; setae on inner expansion of 



basal segment of fifth legs very unequal in length iiorvegica (p. 176) 



Caudal setae nearly twice as long as body ; setae on inner expan- 

 sion of basal segment of fifth legs equal in length rosea (p. 177) 



MICROSETELLA NORVEGICA (Boeck) 



Figure 121 



Setella norvcgica Boeck, Forh. Vid.- 

 Selsk Christiauia, p. 281, 1864. 



Microsetella norvegica Sars, Crustacea 

 of Norway, vol. 5, p. 44, pi. 24,'» 1904. 



Occurreyice. — Ten females from 

 surface tow in Vineyard Sound. 



Distnhution. — British Isles 

 (Brady) ; Atlantic Ocean (Brady 

 and Robertson) ; Arctic Ocean 

 Mrazek) ; Mediterranean (Car, 

 Steuer, Grandori, Pesta) ; tropical 

 Pacific (A. Scott) ; Red Sea, In- 

 dian Ocean (Thompson and Scott) ; 

 Narragansett Bay (Williams). 



Color. — Body yellowish white 

 and transparent, without pigment 

 markings. 



Female. — B o dy almost linear 

 and strongly compressed; head 

 flattened dorsally; rostrum short and turned abruptly downward; 

 segments of urosome with transverse rows of minute spinules ; caudal 

 rami about as wide as long, divergent, the second inner apical seta 

 three-fourths as long as the body. Inner expansion of basal seg- 



FiGUitE 121. — Microsetella norvegica: a. 

 Female, dorsal (after Sars) ; &, female, 

 fifth leg ; o, male, first antenna 



'» This plate bears the label Microsetella atlantica and was not changed to agree with 

 the text. 



