780 FRESH-WATER BIOLOGY 



101 (100) Rami of swimming feet composed of two segments. 



Cyclops bicolor Sars 1863. 



It is not common, but is occasionally seen. The only species with 

 which it is likely to be confused is phaleratus, and the difference in the 

 segmentation of the swimming feet makes the distinction easy, as the 

 rami have only two segments, while in phaleratus they have three. The 

 fifth foot consists of a single segment and bears one spine. 

 Length of female, 0.5 mm. 



FIG. 1 2 29. Fifth foot of Cyclops bicolor. X 450. (Original.) 



102 (99, 103) Antennae composed of eight segments. 



Cyclops fimbriatus Fischer 1853. 



Is the only species with antennae of eight segments, and, if found, can easily be recognized 

 by this characteristic if one is sure that he is examining mature forms. 

 Length of female, 0.7 to 0.84 mm. 



103 (99, 102) Antennae composed of six segments. 



Cyclops aequoreus Fischer 1860. 



Found only in brackish water. It has been found in 

 America in waters connected with the Gulf of Mexico, 

 and those connected with the Pacific Ocean in Panama. 



FIG. 1230. Abdomen and fifth feet of female Cyclops aequoreus. 

 X73- (Original.) 



104 (i) Cephalothorax and abdomen not distinctly separated, so that the 



whole body is somewhat worm-like; antennae short, never 

 composed of more than eight segments. 



Family HARPACTICIDAE . . 105 



All species of Harpacticidae are very minute. Only a few species have been described and 

 those very inadequately. Probably there are many undescribed species and other genera 

 than those mentioned. 



105 (108) Antennae composed of six segments, endopodites of all swimming 



feet composed of two segments, segments of endopodite of 

 fourth foot fused so as to appear as one, endopodite of first 

 foot slightly elongate; found in fresh and brackish waters, 

 in New Mexico Marshia . . 106 



1 06 (107) Furca of female two and one-half times as long as broad, furca of male 



four times as long as broad, median furcal setae fused at base. 

 Marshia albuquerquensis Herrick 1895. 



107 (106) Furcae of female and male twice as long as broad, median furcal 



setae not fused at base. . Marshia brevicaudata Herrick 1895. 



108 (105) Antennae composed of eight segments, endopodites of swimming 



feet composed of two or three segments, endopodite of third 

 foot usually much longer than exopodite, endopodite of male 

 fifth foot always of three segments. 



Canthocamptus . . 109 



