210 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



Genus PSEUDOTHALESTRIS Brady, 1883 



Body short and stout, somewhat pear-shaped ; head fused with the 

 first segment, very large and highly vaulted dorsally; urosome 

 sharply defined from the metasome, 4-segmented and much-tapered 

 posteriorly; caudal rami nearly twice as wide as long. First an- 

 tennae 5- to 7-segmented, slender; exopod of second antennae 

 3-segmentecl ; exopod of first legs 2-segmented, sometimes the two 

 segments fused ; endopod and both rami of the three following pairs 

 of legs 3-segmented; second endopod modified in male; fifth legs 

 2-segmented, of (he usual form in female, somewhat modified in 

 male. Ovisac single and pear-shaped. 



KEY TO THE SPECIES (BOTH SEIXES) 



1. Small ; first antennae slender and elongate, 6- or 7-segmented ; 



two segments of first exopod distinctly separated 2 



Much lai-ger ; first antennae only 5-segmented, short and stout ; 



segments of first exopod fused nobilis (p. 210) 



2. First antennae 6-segmented ; inner expansion of basal segment of 



fifth legs reaching to or beyond tip of distal seg- 

 ment minuta (p. 211) 



First antennae 7-segmented ; inner expansion of basal segment of 



fifth legs not reaching beyond base of distal segment pygmaea (p. 212j 



PSEUDOTHALESTRIS NOBILIS (Baird) 



Figure 140 



Arpacticus nohilis Baird, The natural history of the British Entomostraca, p. 



214, pi. 28, fig. 2, Or-e, 1850. 

 Westiooodia nobilis Saks, Crustacea of Norway, vol. 5, p. 140, pis. 85, 86, 1906. 



Occurrence. — Fifteen females from Penzance Pond, Woods Hole, 

 August, 1925 ; 15 males and females from Little Harbor, Woods Hole, 

 September, 1881 ; a single female from one of the brackish ponds on 

 Chappaquiddick Island, July, 1926. 



Distribution. — British Isles (Baird, T. Scott, Brady) ; Helgoland 

 (Glaus) ; coast of France (Canu) ; coast of Bohusliin (Cleve) ; 

 Lofoten Islands (T. Scott) ; coast of Norway (Sars) ; Adriatic (Car, 

 Graeffe, Grandori, Pesta) ; Gulf of Genoa (Brian). 



Color. — Body light yellowish brown, ornamented with a very varie- 

 gated pattern of deep brownish-red pigment, especially noticeable in 

 lateral view ; eye dark ruby red. 



Female. — Body robust; metasome considerably compressed, epi- 

 meral plates of moderate size and rounded at the corners; rostrum 

 broadly triangular, sharply pointed and depressed ; urosome less than 

 half the length of the metasome; genital segment divided laterally; 

 caudal rami twice as wide as long, the two middle apical setae 

 enlarged and elongated. First antennae 5-segmented, stout; inner 



