COPEPODA 



343 



the thorax and 24-jointed; fifth feet uniramose: 7 species; in fresh^ 

 brackish, and salt water. 



E. hirundoides (Nordquist) (Fig. 537). Last thoracic segment of 

 female with 2 large projections; length 1.16 mm.; transparent, with yel- 

 low bands: Gnlf of Mexico and its estuaries, abundant; 

 Boston and Narragansett Bays; Europe. 



6. Epischura Forbes. Thorax of 5 segments; abdo- 

 men 4-jointed in female, in male 5-jointed, asymmetrical 

 and with prehensile processes on right side; first 4 pairs 

 of legs biramose, the outer branch 3-jointed, the inner 

 branch 1-jointed; fifth pair uniramose, prehensile in male: 

 3 species; in fresh water. 



E. lacustris Forbes. Length 1.7 mm.; second ab- 

 dominal segment as long as the rest of the abdomen: in 

 deep lakes; central and western America. 



7. DiAPTOMTis* Westwood. Thorax usually of 5 seg- 

 ments; abdomen of male with 4, female with 3 segments; first antennae 

 with 25 joints; inner branch of first pair of legs 2-jointed, outer branch 

 3-jointed; both branches of legs 2 to 4 are 3-jointed; fifth pair irregular 

 in form, the inner branch being often rudimentary, the outer branch 

 usually 4-jointed ,in the female, and 5-jointed in the male: about 80 

 species, of which 34 are American; in fresh water. 



Fig. sris 



Fig. 539 



Fig. .538 — Diaptomus oregonensis (Pearse). A, dorsal aspect of female; B, fifth 

 leg of female ; C, fifth leg of male. Fig. 539 — Diaptomus Icptopus. A, lateral aspect 

 of body (Ilerrick) ; B, fifth leg of female. 



D. oregonensis Lilljeborg (Fig. 538). Body small, 1.5 mm. long; 

 first abdominal segment of female expanded and equal in length to rest 



* See "The North Am. Species of Diaptomus," by F. W. Schacht, Bull. 111. St. Lab., 

 Vol. 5, p. 97, 1897. "A revision of the North Am. Species of Diaptomus," by C. D, 

 Marsh, Trans. Wis. Acad. Sci., Vol. 15, p. 381, 1907. 



