THE WATER FLEAS (CLADOCERA) 



703 



64 (63) Vertex angulated, with spines. 



Antennules long. 



Ceriodaphnia rotunda Sars 1862. 



General form much like preceding. Head angled at vertex, 

 with spines. Antennules long and slender. Post-abdomen 

 somewhat enlarged, but not so much as in laticaudata, tapering 

 toward apex, obliquely truncate, with 7-9 slender anal spines. 

 Color j'ellowish or brown, not transparent. Length, 2, to 

 i.o mm.; 3" -to 0.6 mm. 



Rare, Wisconsin. Both this species and the preceding live 

 among weeds. 



Fig. 1088. Ceriodaphnia rotunda. (After Lilljeburg.) 



65 (49) Head large and usually extended. Antennules large and freely 



movable. Post-abdomen with post-anal extension. . . 66 



66 (67) Body compressed. Valves elliptical, crested dorsally, completely 



covering body. Ocellus present. Fornix and abdominal 

 process well developed. . . . Moinodaphnia Herrick 1887. 



Cervical sinus present; no cervical gland. Valves tumid in postero-dorsal region; crested; 

 minute spines on ventral margin; sharp angle, not spine, at junction of dorsal and ventral 

 margins; marked with oblique striae, usually invisible in preserved specimens. Antennules 

 attached on ventral surface of head, sense-hair about middle; olfactory setae small. One large 

 abdominal process, broad, concave in front, somewhat saddle-shaped, forming a transition to 

 the condition in Moina. Post-abdomen as in Moina, with slender post-anal projection bearing 

 about 10 finely ciliate spines and a much longer distal spine with 2 unequal prongs, the bident 

 (Fig. 1094). Claws denticulate. Summer eggs numerous. Male (South America) much like 

 Moina, with large curved antennules. 



Only one certain species. . Moinodaphnia madeayii (King) 1853. 



Color yellowish, transparent. 

 Length, 9 » ca. r .0 mm. 



Louisiana. In weedy pools 

 and lakes. 



Herrick's M. alabamensis is re- 

 ported as larger (1.68 mm.) and 

 may possibly be a different spe- 

 cies. Herrick had only King's 

 very imperfect description for 

 comparison with his form, and 

 his own description is correspond- 

 ingly imperfect. Sars' figures of 

 M. macleayii from Brazil show a 

 form identical with that from 

 New Orleans. 



Fig. io8g. Moinodaphnia macleayii. 



67 (66) Body thick and heavy. Valves somewhat rhomboidal, not wholly 

 covering body. Fornix small. Ocellus absent. Abdominal 

 process represented by horse-shoe shaped fold. 



Moina Baird 1850 . . 68 



Cervical sinus present. Valves thin, obscurely reticulated or striated; no posterior spine. 

 Head large, thick, rounded in front; sometimes with deep depression above eye; no rostrum. 

 Antennules long, spindle-shaped, freely movable; lateral sense-hair about middle. No regular 

 abdominal projection, but in old 9 a horse-shoe shaped ridge which closes the brood-cavity. 

 Post-abdomen extended into conical post-anal part, bearing ciliated spines and bident. Claws 

 small; abdominal setae very long. Summer eggs numerous; ephippium oval, with i or 2 eggs. 

 Antennule of $ very long and stout, modified into clasping organ; denticulate, with small 

 recurved hooks at apex. First foot with hook. 



The species of Moina ordinarily inhabit muddy pools and similar places. They are soft- 

 bodied, weak creatures; liable to be much distorted by preserving fluids. The species are much 

 alike and often hard to distinguish unless $ and ephippial J ate present. 



O.I MM. L 



