214 



BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



Found in great abundance in Penzance Pond, Woods Hole, and 

 Sengekontacket Pond, Marthas Vineyard. 



Distribution. — British Isles (Brady, Bourne) ; coast of Bohuslan 

 (Cleve) ; Mediterranean (Claus) ; coast of Norway (Sars) ; North 

 Sea (Timm) ; Adriatic (Car, GraefFe, Steuer, Grandori, Pesta) ; 

 Wickford, Charlestown Pond, K. I. (Williams); Woods Hole 

 (Sharpe), 



Color. — Entire cephalothorax, the tips of the swimming legs and 

 the ovisacs golden yellow faintly washed with brown; remainder of 



body and appendages light 

 brown, often tinged with blue; 

 eggs pale blue; eye bright red. 

 Female. — Cephalic segment 

 about half the body length, 

 strongly compressed, the epi- 

 meral portions turned down- 

 ward and inclosing the mouth 

 parts ; rostrum very prominent, 

 curved downward, and blunt at 

 the tip; genital segment di- 

 vided, the anterior half dilated ; 

 caudal rami close together, 

 their apical setae nearly paral- 

 lel. First antennae very long 

 and slender; basal expansion 

 of fifth legs reaching beyond 

 the tip of the distal segment, 

 tongue-shaped, with three apical setae and two on the inner margin ; 

 distal segment twice as long as wide with six unequal setae, the inner 

 and three outer ones plumose, the other two slender and hairlike. 

 Total length, 0,7-0,9 mm. 



Male. — First antennae prehensile, the five distal segments turned 

 outward; second basipod of first legs with a small inner lappet; 

 endopod of second legs scarcely as long as the basal exopod segment, 

 its distal segment subspherical, with a curved apical spine and an 

 outer setiform spine, both denticulate; segments of fifth legs com- 

 pletely fused, basal expansion with two unequal setae, distal portion 

 with four setae, the second outer one hairlike; rudimentary sixth 

 legs present. Total length, 0.&-0.7 mm. 



Remarks. — This species may be distinguished by the prominent 

 rostrum, the long antennae, and the details of the fifth legs. It 

 frequents the littoral zone among algae, and it is frequently left in 

 tide pools. 



Figure 143. — Diosaceus tenuioornis: a. Fe- 

 male, dorsal (after Sars) ; i, female, fifth 

 leg ; c, male, fifth and sixth legs ; d, male, 

 second leg 



