338 



BULLETIN" 15 8, tJKlTED STATES NATIONAL MUSEUM 



KEIY TO THE SPECIES (FEMALES) 



1. Outer margin of caudal rami coarsely toothed, the teeth increas- 

 ing in length distally ; outer seta close to tip agilis (p. 338) 



Outer margin of caudal rami smooth, without teeth; outer seta 



near center of outer margin prasinus (p. 339) 



EUCYCLOPS AGILIS (Koch) 



FiGUBE 201 



Cyclops agilis Koch, Deutschlands Crustaceen, Myriapoden und Arachniden, 



pt. 21, pi. 3, 1838. 

 Leptocyclops agilis Sars, Crustacea of Norway, vol. 6, p. 71, pi. 43, 1914. 



Occurrence. — Found in greater or less abundance in all the fresh- 

 water ponds in and around Woods Hole and along Cape Cod to 

 Chatham, in Edgartown Great Pond and two small ponds on Marthas 



Vineyard, and in most of the 

 fresh-water ponds on the Eliza- 

 beth Islands. 



Color. — Body dark olive-green, 

 banded across the thorax, the 

 genital segment and the bases 

 of the caudal rami with reddish 

 brown. Eye bright red. Eggs 

 light bluish white. 



Distribution. — Europe ; central 

 and northern Asia; Algeria; 

 Azores; polar islands north of 

 Grinnell Land; North Amer- 

 ica; Australia; New Zealand 

 (Brady); Nantucket Island 

 (Pearse) ; Khode Island (Wil- 

 liams). 



Female. — Metasome elliptical, 

 width slightly more than half the 

 length; urosome less than half the length of the metasome; genital 

 segment as long as the first two abdominal segments combined; 

 caudal rami twice the length of the anal segment, curved slightly 

 outward, their outer margins denticulate, the teeth increasing in 

 size distally, the outer seta close to the tip of the ramus. 



First antennae reaching the distal end of the second metasome 

 segment, the last three segments with a smooth lateral membrane. 

 Outer spines on first four exopods 3, 4, 4, 3; inner spine of fifth 

 leg as long as outer one and coarsely dentate. Anterior portion of 

 semen receptacle transversely elliptical and slightly emarginate at 

 the center; posterior portion also emarginate at the center and 



Figure 201. — Eucyclops agilis: a, Male, 

 dorsal ; h, c, male, fifth and sixth legs ; 

 d, anal segment and caudal ramus 



