STATE GEOLOGIST. 35 



foot of the male is furnished with a long bristle; the lower shell 

 margins are more bristly thaa in the previous forms; the ephip- 

 pium has two cavities, while the seminal bodies are crescent-shaped. 



Sp. 3.— Moina micrura, Kurz 



This form may bn of specific value, but it is Dot suffi^^iently dis- 

 tinguished to make this certain. As described by Kurz, it seems to 

 be smaller (1 ram.) and most to resemble M. paradoxa, which was 

 not at that time described. The post-abdomen is short and has few 

 •(6) spines, while the terminal claws are short and smooth; the 

 bead has a sinus above the eyes; the eyes are smaller, with numer- 

 ous lenses; the antennules are shorter (?) than in M. rectirostris; 

 the mandibles are partly exposed, while the shell margin overlying 

 is notched. Males and ephippial females were not observed. Not 

 distinguished in America. 



II. — Genus Ceriodaphnia, Dana. 



The genus Ceriodaphnia is the successor to Moina, which some 

 «pecies greatly resemble; the post-abdomen, however, is shorter 

 •and has a habitus resembling Daphnia; the antennge are smaller, 

 ^nd the shell is thick and coarsely reticulated. 



Ceriodaphnia has the same general mode of life as Moina, living 

 in muddy pools 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 antennae show a transi- 

 tion in the various species from forms adapted for prehension to 

 «uch 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 but 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 pres- 

 -ent; beak absent; antennules moveable, rather short; antennae with 

 the three-Jointed ramus with five setae; first foot of the male with 

 a hook or flagellum. 



The members of this genus are danger signals from a hygienic 

 point of view, for they frequent water containing decaying matter; 

 as many as 1,400 were counted in a single quart of such water. 

 The genus is particularly perplexing, as the varieties named seem 

 to be hardly entitled to specific rank and are so similar as to re- 

 quire great care to properly distinguish. 



