4 Trans. Acad. Sci. of St. Loins 



marsh where about two inches of water rested upon 

 more than two feet of water-soaked silt. Originally this 

 marsh was a reservoir which had })een constructed on a 

 shelf-like depression between two hills. In addition to 

 receiving the wash from the surrounding hills, this pond 

 was fed by a spring which furnished sufficient water to 

 cause a continuous overflow through the spillway of the 

 dam. The fine materials washed from the surrounding 

 hills have gradually transformed this reservoir into a 

 marsh Imt the water continues to flow out through the 

 spilhvay. It was near this spillway that the specimens 

 were found. A group of cattails, which has been gradual- 

 ly increasing in size since the day when it was sur- 

 rounded by water many inches deep, still flourishes, and 

 patches of duckweed are scattered over the surface of 

 the marsh. At the time the specimens were found the 

 temperature of the water was 25°C., the temperature of 

 the surrounding atmosphere being over 32°C. The PH 

 of the water was 7.6. 



Associates. — The following Entomostracans w^ere 

 found associated with it: Bosmina longirostris (0. F. 

 Mueller), Ceriodaphnia rigaudi Richards, Cyclops 

 lenckarti Glaus. In May Cyclops alhid}<s Jurine var. 

 tenidcornis was found in the same place; also Cyclops 

 viridis Jurine. A species of Vorticellidae was found as 

 a commensal, attached to the abdomen, among the eggs 

 (pi. 2, fig. le). 



Preliminary List of Copepoda and Cladocera of 



St. Louis District 



In this communication no attempt is made to give a 

 complete list of synonyms ; such lists will be found in the 

 references mentioned. For easy reference, the genera 

 and species are arranged in alphabetical order under 

 each familv. 



