204 



BULLETIN" 15 8, UNITED STATES NATIONAL MUSEUM 



Genus MICROTHALESTRIS G. O. Sars, 1905 



Body slender and subcylindrical, the iirosonie not sharply defined 

 from the metasome; head fused with the first segment, the epimeral 

 portions rather insignificant, but turned downward and partially 

 inclosing the mouth parts; urosome 4-segmented and slightly tapered 

 posteriorly; genital segment distinctly divided; caudal rami wider 

 than long, inner apical seta two-thirds as long as the entire body. 

 First antennae 9-segmented ; exopod of second antennae 2-segmented ; 

 endopod of first legs 2-segmented, exopod and both rami of the three 

 following pairs of legs 3-segmented; fifth legs 2-segmented in 

 female, 4-segmented in male. 



KEnr TO THE SPECIES (FEMALES) 



1. Distal segment of fifth legs with 8 setae, 2 apical and very un- 



equal, 3 on outer and 3 on inner margin forficula (p. 204) 



2. Distal segment of fifth legs with 6 setae, 2 apical and subequal, 



3 on outer and 1 on inner margin littoralis (p. 205) 



MICROTHALESTRIS FORFICULA (Glaus) 



Figure 135 



Thalestris forficula Claus, Die frei lebenden Copepoden, p. 131, pi. 17, 1863. 

 Microtlialestris forficula Sars, Crustacea of Norway, vol. 5, p. 123, pi. 76, 1905. 



ccurren ce. — T wenty 

 specimens, including 

 both sexes, were ob- 

 tained i n Penzance 

 Pond, Woods Hole, 

 August, 1925. 



D ist7^huf{on.' — Med- 

 iterranean (Claus) ; 

 British Isles (T. 

 Scott) ; coast of Bo- 

 husliin (Cleve) ; Spitz- 

 bergen, Franz Josef 

 Land (T. Scott) ; Po- 

 lar islands, coast of 

 Norway (Sars). 



Color. — Body trans- 

 parent and of a uni- 

 form pale yellow ; ova- 

 ry, oviducts, and eggs 

 whitish; eye dull red. 

 Female. — Body narrow and elongated, four and one-half times 

 as long as wide; cephalic segment short, somewhat compressed, its 

 epimeral parts turned downward and inclosing the bases of the 

 mouth parts; urosome cylindrical, each of its segments with a 



FiGtiRE 135. — llicrothalcstris forficula: a, Male, endopod 

 of third leg; h, female, fifth leg; c, male, fifth leg; d, 

 male, first leg 



