666 FRESH-WATER BIOLOGY 



together with diatoms, other algae, and Protozoa. Large species, 

 however, are able to gnaw objects, and Apus is said to nibble 

 insect larvae and tadpoles. No parasitic phyllopods are known. 



The distribution of all species is apt to be local and irregular. 

 A certain pool may swarm with phyllopods, while others near at 

 hand will not possess a single individual. A particular species may 

 be extremely abundant for one season and then be infrequent or 

 entirely absent for several years, or it may appear regularly in a 

 certain spot season after season. No Notostraca have been found 

 in eastern United States and none of the genus Estheria in the 

 Conchostraca are found east of the Mississippi River. The greater 

 part of the North American species are found on the great plains. 



Collecting phyllopods is usually a simple matter. They are 

 easily captured with a hand net or picked up with the fingers. 

 For ordinary purposes 70 per cent alcohol is a satisfactory preserv- 

 ative; specimens may be kept for future reference by dropping 

 them into it and keeping them in a tightly stoppered bottle. Dilute 

 formol may also be used, but is not as satisfactory as alcohol because 

 it often makes specimens so brittle that they break up easily. 

 These crustaceans are admirable aquarium animals and make 

 attractive objects for a school room or private study. With a 

 few water plants for company they may Hve for weeks. They 

 should not be put in aquaria with predaceous animals for usually 

 they will be quickly devoured. 



ElEY TO NORTH AMERICAN FRESH-WATER PHYLLOPODA 



1(36) Body elongated, without carapace (Fig. loii) . Suborder Anostraca . 2 



2 (5) Seventeen to nineteen pairs of pregenital ambulatory limbs. 



Family Polyartemudae. 

 Only one genus in America Polyartemiella. . . 3 



3 (4) Male frontal appendage tuberculiform ; male clasping antenna quadri- 



ramose Polyartemiella hanseni (Murdoch) 1874. 



Described from Alaska. This and the following species are remarkable 

 for the large number of ambulatory limbs which exceeds that of any other 

 anostracan. Apparently common in portions of Alaska and Yukon 

 Territory that border on the Arctic Ocean. 



Fig. 1015. Polyartemiella hanseni. Side view of head of male. X 6. 

 (After Daday.) 



