THE WATER FLEAS (CLADOCERA) 



693 



18 (3) Enclosed in gelatinous mantle. Antennae simple in female, cylindrical, 

 with 3 terminal setae Family Holopedidae Sars. 



Animal enclosed in a large, globular, transparent, delicate but tough, gelatinous case, open 

 ventrally and forming 2 valves. Body much compressed, shell of head and body very thin and 

 high, as seen from side, leaving uncovered the mouth parts, the ends of the feet, and the hind 

 part of body. Antennule small, fixed; with 5-6 olfactory setae and lateral sense-hair, but no 

 flagellum. Antennae in 9 long; basal joint curved, annulated; the single ramus 2-jointed; 

 antennae of $ biramous. Post-abdomen large, 

 fleshy, not bent forward; with rather long, 

 curved anal spines and clusters of very fine 

 spinules; abdominal setae long, set on single, 

 long, conical projection. Claws large, curved, 

 denticulate, not set off from body by distinct 

 joint. Eye small, with numerous lenses; ocellus 

 small. Intestine simple with 2 hepatic ceca. 

 Branchial sac on second to fifth feet. Color 

 transparent. Swims on its back. 



Sole genus with characters of family. 

 Holopedium Zaddach 1855 . . 19 



19 (20) Ventral margins of valves 

 with fine spines. 

 Holopedium gibberum Zaddach 1855. 



Post-abdomen elongated (ca. one-third 

 length of body) and tapering; anal spines 

 nimierous, up to 20. Claws with i 

 basal spine. Length, J, i.s-2.2 nun.; 

 J , 0.5-0.6 mm. 



This remarkable and beautiful species 

 is not uncommon in open water in 

 northern lakes; has been found in the 

 Great Lakes, and in many inland waters, 

 both lakes and smaller bodies of water. 



Figs. 1060, 1061, a. Holopedium gibberum 

 (gelatinous case not shown). (See also 

 Fig. 1061.) 



0.S MM. 



20 (19) Ventral margin of valves smooth. 



Holopedium amazonicum Stingelin 1904, 



Post-abdomen short, blunt (ca. 

 one-fourth of body in length), with 

 7-8 anal spines, the row continued 

 forward by 3-4 very small spinules. 

 Claws without basal spine. Abdom- 

 inal setae very long and 3-jointed. $ 

 unknown. Length, $, i.o mm. Lake 

 Charles, Louisiana. 



Fig. 1061. a, Holopedium gibberum, 

 b, Holopedium amazonicum. 



