96 U.S. NATIONAL MUSEUM BULLETIN 23 6 



Males differ from females in following points : Antennules 8- to 9- 

 segmented, subchirocerate, 5th segment strongly swollen, with aes- 

 thetasc, apical 3 or 4 segments fused. Endopodites of legs 2 and 3 

 modified, though still 3-segmented. 2nd endopodal segment of leg 2 

 drawn out to sharp point, reaching half length of 3rd endopodal 

 segment, 1 internal seta. 3rd endopodal segment of leg 2 also drawn 

 out to point, bifid at apex, with 2 internal setae. 2nd endopodal seg- 

 ment of leg 3 with spiniform process at internal part of apex, fitting 

 into depressed part of 3rd endopodal segment; 2nd endopodal segment 

 with 1 internal; 3rd with total of 6 setae. Exopodite of leg 5 almost as 

 in female, number of setae not reduced. Only 2 setae occur on the 

 much shorter baso-endopodite. 



Type species: Perissocope typicus Brady 1910 {=Harpacticus sim- 

 plex Brady, 1910). 



Further species: Harpacticus cristatus A. Scott, 1909; H. xenus 

 Monard, 1926, Perissocope littoralis Lang, 1934, and P. bayeri, new 

 species, to be described below. 



Key to the Females of Perissocope 



1. Cephalic somite longitudinally carinated; of the setae on the exopodite of leg 



5 (5 in all) two are broadened, dagger-shaped ... P. cristatus (A. Scott) 



Cephalic somite smooth ; all setae on the exopodite of leg 5 (numbering 5 to 7) 



are normally developed and slender 2 



2. Exopodite of leg 5 with 7 setae P. typicus Brady 



Exopodite of leg 5 with 5 or 6 setae 3 



3. 3rd exopodal segment of leg 4 with 2 spines at external margin; setae on 



exopodite of leg 5 number 5 P. bayeri, new species 



3rd exopodal segment of leg 4 with 3 spines at external margin; setae on 

 exopodite of leg 5 number 6 4 



4. Terminal segment of exopodite legs 3 and 4 with 2 internal setae, total number 



of appendages on these segments 7 P. xenus (Monard) 



Terminal segment of exopodite legs 3 and 4 with 3 internal setae, total number 

 of appendages on these segments 8 P. littoralis Lang 



Perissocope bayeri, new species 



Figures 31-33 



Material.— Loc. 589, 4 ad. 99, 0.27-0.32 mm. (0.29 mm.); 1 ad. d", 

 0.29 mm. 



Description. — The following has been taken from an adult, 

 ovigerous female, 0.30 mm. length (holotype), which has been dis- 

 sected and mounted. The male allotype also has been dissected and 

 mounted. The remaining three females have been labelled as 

 paratypes. 



Adult female, total length 0.30 mm.; maximal diameter 0.11 mm.; 

 length of longest furcal seta 0.12 mm. 



