ENTOMOSTKACA OF MINNESOTA. 167 



with the fauna of the southern hemisphere. The species is large 

 compared with Ilonia, being 1.68 mm. long. The head is shaped much 

 as in Simocephalus, being acutely rounded in front of the eye and pro- 

 vided with a distinct beak, near which the antennte are attached. The 

 eye is large and the fornix evident, as in Baphnia. The antennules are 

 long and slender, little narrowed apically, armed with a fiagellum at 

 the basal third. Antennae slender, segments narrow; apical segment 

 of four-jointed ramus has in addition to the three geniculate seti^e a 

 very long spine representing the short thorn occupying that place in 

 Moina, otherwise as in that genus. Body quadrangular, somewhat 

 produced above at the posterior angle. Lower margin armed with 

 short spines as in Daplmia. Abdomen slender, claw slightly curved 

 and armed with a continuous series of small set®. A short spine in 

 front of the claw. Lateral spines as in Moina, twelve or more in num- 

 ber, the first being bifid. Dorsal part of abdomen with a long process 

 for occluding the brood sac, also a blunt tuberosity caudad of it. The 

 general habitus is like Moina, but in the form of the shell and many 

 details it approaches Daphnia. The description of King's species is 

 not full enough to make si)ecific comparison possible, but of the generic 

 relationship there can be no question. The most important diagnostic 

 difference — that in the formula of the antennary spines — not funda- 

 mental but a mere matter of proportions. 



GENUS CERIODAPHNIA Dana. 



The genus Ceriodaphnia is the successor to Moina, which some species 

 greatly resemble; the post-abdomen, however, is shorter and has a 

 habitus resembling Daphnia; the antennae are smaller and the shell is 

 thick and coarsely reticulated. 



Geriodaphnia has the same general mode of life as Moina, living in 

 muddy j)ools in late summer and bearing numerous broods which often 

 greatly extend the brood cavity. The antennules are shorter but have 

 a similar form; the male antennte show a transition in the various 

 species from forms adapted for prehension to such as are found in 

 Daphnia. The brood cavity is closed by two ridges on the abdomen 

 instead of one, as in Moina, or three, as in Daphnia. 



The ephippium contains bnt a single ovum. In general, the form 

 is oval or quadrate, angled but not spined posteriorly; head separated 

 from the body by a deep depression; pigment fleck present; beak 

 absent; antennules movable, rather short; antennae with the three- 

 jointed ramus with five setae; first foot of the male with a hook or 

 fiagellum. 



