STATE GEOLOGIST. 103 



the carapax in length, but at each successive moulting the spine is found to be 

 shorter. The upper part of the body has four projections, one of which is longer 

 than the others and serves evidently to keep the ova in position. 



Dr. Baird says that " the male is much smaller than the female", which is the 

 case in nearly all the species, "and the superior antennae are much larger and 

 spring from under the beak instead of from the beak itself. The inferior extrem- 

 ities of the valves are more densely serrated than in the female." 



The males are always fewer than the females. The motions of this creature 

 are quick, spasmodic leaps through the water, and it often presents a beautiful 

 appearance. 



Daphnia Vetula. 



Bibliograjohy. — Daphne vetula, Muller, Zool. Dan. Prod., No. 2399. 



Daphnia vetulo, Straus, M^m Mus. Hist. Nat., V., t. 29, f. 25-6. 



Baird, Ann. Mag. Nat. Hist., i., 255, t. 9, f. 13. 



Daphnia sima, MulUr, Entomost., 91, t. 12, f. 11-12, 1785. 



Latreille. 



Bosc. 



Ranidohr. 



■ Gruithuisen. 



Desmarest. 



Lamarck. 



M. Edwards. 



^Koch. 



Monoculus sima, Givelus. 



Manuel. 



Jurine. 



* Monoculus IsBvis, Fdbricius. 



Monoculus expinosus, De Geer. 



Monoculus conchacus, Donovaan. 



Ungeschwauzter-zackiger, Wasserfioh, Schoeffer. 



Monoculus nasutus ( ?) Jurine. 



Monoculus pulex, Sulger. ^ 



Daphnia congener, Koch. 



Daphnia expinosa, Koch. 

 Description. — In size like Daphnia pulex, some forms of which it resembles. 

 Carapax in the male quadrangular with the sides nearly parallel, the posterior 

 prominence being near the dorsal part of the shell. In the female, however, the 

 prominence is near the middle of the posterior side, while the carapax is widest 

 near that extremity. The spine usually present in the larger Daphnidse is obso- 

 lete, but there is a series of small spines or teeth on the upper posterior margin. 

 The lower edge is strongly ciliated. The carapax is strongly lined transversely. 

 These striae arise from the one or two rows of hexagonal cells which border' the 

 lower margin, and anastomose occasionally, giving in some cases a reticulated 

 appearance to the sheU. The head is veiy small proportionately, rounded in 

 in front, and rather strongly beaked below. 



The superior antennae are quite evident. Inferior antennae large. The first 

 joint is fleshy and stout, margined at the extremity with spines and sending out 

 three branches, of which the two large swimming organs are as in pulex, having 

 the plumose setae, etc. At the base and between these is a third, consisting, of a 

 conical pomt with a broadened base ending in a spinous appendage. The scuta 



