338 CLASS CRUSTACEA. 



culi of Juvine, his second family. The form oftvro of their 

 antennae, which resemble two ramified arms, serving as oars, 

 and the faculty which they have of jumping, have caused 

 one of their most common species to be called the arho- 

 rescent aquatic Jlea. 



The first of these naturalists, who has given us an excellent 

 monograph of Daphnia, a subgenus of this division, has esta- 

 blished two new ones, one under the denomination of La- 

 TONA, having as character, the antennae in the form of oars, 

 divided into three branches, and of a single articulation ; 

 {Daphiiia SeUfera^'MviW.) and the other that of SiDA, approxi- 

 mating to the known subgenera of the same division, with 

 relation to the same antennae, divided only into two branches, 

 but one of which has two articulations, and the other three. 

 {Daphnia cristallina, Milll.) According to him, the daphnia 

 should be distinguished from the preceding, and from the 

 lyncete, by one of the two branches of the oars being composed 

 of three articulations, and the other of four. Nevertheless, 

 Jurine (Hist, des Mon. p. 92.) says, that each branch is com- 

 posed of three articulations ; but it appears that he took no 

 account of the first of the posterior branch, which is indeed 

 very short. The last in all those lophyropa, is terminated by 

 three filaments, and each of the preceding gives out another. 

 These filaments are simple or barbed. There exist also two 

 other antennae, but very short, especially in the females, 

 situated at the anterior and inferior extremity of the head, 

 and which have but a single articulation, with one or two 

 setae at the end. 



Polyphemus, Mull., 



Have, as well as daphnia and lynceus, their antennae in the 

 form of oars, divided into two branches ; but each of them' is 

 composed of five articulations. Moreover, their head, very 

 distinct, and rounded, supported on a sort of neck, is almost 



