6 Trans. Acad. Sci. of St. Louis 



on the antenna is smooth, in others finely serrated. Found in both fetid 

 water and in water having no perceptible odor. April, May and July. 

 ». CYCLOPS ALBIDUS Jurlne 1820, var. CORONATUS. 



Cyclops aignatus, var. coronatua, Herrick & Turner, '95. p. 106. pi. 

 15, fig. 1-4. 

 Found only once in this district, among cattails in a shallow pond, the 

 temperature of which was 21''C. 



10. CYCLOPS BICUSPIDATUS Claus 1857. 



Cyclopa forbeai, Herrick & Turner, '95. p. 104. 



Cyclops bicuapidatua, E. B. Forbes, '97. pp. 44-47. pi. 12, fig. 1-4. 

 Found in this district in four different no-outlet ponds free from vege- 

 tation, but once only in each place. In one pond the temperature waa 

 17''C. ; in another 19° ; temperature of the others not recorded. The hydro- 

 gen ion content of one pond only was measured, the PH value being 7.2. 

 April and October. 



11. CYCLOPS FIMBRIATUS Fischer 1853. 



Cyclopa fimbriatua, Herrick & Turner, '95. pp. 121, 122. pi. 17, flg. 

 8. 9; pi. 21, fig. 11; pi. 25. fig. 9-14. 

 This form is rare here, it having been collected but once, June 1, 1921, 

 when I obtained a few from a shallow temporary pond with a PH value 

 of 8.2. 



12. CYCLOPS FUSCA Jurlne 1820. 



Cyclopa aignatus, var. coronatua, Herrick & Turner, '95. p. 106. pi. 

 U. 

 I have always considered this a variety of C. albidua and have discussed 

 it under that head. 

 18. CYCLOPS PHALERATUS Koch 1863. 



Cyclops phaleratua, Herrick & Turner, '95. pp. 120, 121. pi. 17, fl^. 



1-7 ; pi. 18, fig. 2, 2d ; pi. 19, fig. 1 ; pi. 21, fig. 6-10. 

 Cyclops phaleratua, E. B. Forbes, '97. pp. 59-63. pi. 20, fig. 8. 

 A few found on one occasion in a no-outlet pond, the temperature of 

 which was 32 *C. Also found in a weedy marsh with PH value of 8.2. 



14. CYCLOPS LEUCKARTI, Claus 18i57. 



Cyclops leuckarti, Herrick & Turner, '96. pp. 96-98. pi. 16; pi. 18, 



fig. 1 a-J; pi. 24, fig. 2-6. 

 Cyclops edax, Forbes, '97. pp. 33-36. pi. 9, fig. 1-8. 

 Collected from three different localities in this district. Two were 

 vegetationless no-outlet ponds, the other a weedy marsh. The temperature 

 of the water and the hydrogen ion content were determined for only one 

 locality, the temperature being 2'5''C. and the PH value 7.8. May, June and 

 August 



15. CYCLOPS, SERRULATUS Fischer 1860 



Cyclops aerrulatus, Herrick & Turner, '95. pp. Ill, 112. pi. li. fl». 



8-11. 

 Cyclops aerrulatua, E. B. Forbes. '97. pp. 64-57.pl. 17 ; pi. 11. 

 fig. 1-3. 

 One of the most widely distributed copepods in this district. Found 

 throughout the season in all types of habitat, at all temperatures and In 

 waters with hydrogen ion content varying from PH 7.00 to PH 8.2. 



16. CYCLOPS VIRIDIS Jurlne 1820, var. INSECTUS Forbes 1882. 



Cyclopa inaectus, Forbes, '82. p. 649. pi. 9, fig. 6. 



Cyclops viridis, var. americanus, Herrick & Turner, '9i5. pp. 91. 



92. pi. 14. fig. 1-9. 

 Cyclops viridia var. insectus, E. B. Forbes, '97. pp. 41-44. pi. 11. 



flg. S-6. 



Perhaps the most common copepod in this district, occurring in all type* 

 of habitat, at all seasons and temperatures, and in waters with the hydro- 

 gen ion content ranging from PH 7.0 to PH 8.2. This and certain speeles 

 of Vorticellldae and of one-celled green algae are often commensals. 



