ORDER BRANCHIOPODA. 351 



the body is almost filiform, composed of a head separated 

 from the trunk by a sort of neck ; of a trunk or thorax, 

 hollow underneath, in its length, divided, at least above, the 

 neck not comprized, into eleven segments, each supporting, 

 a pair of branchial feet, very much compressed, generally 

 composed of three lamellate articulations, with the edges fur- 

 nished with a fringe of hairs, or barbed filaments ; and of 

 an elongated tail, going into a point, consisting of nine seg- 

 ments, terminated by two leaflets, more or less elongated, and 

 bordered with cilise. The under part of its second segment 

 presents the male sexual organs, and in the female an elongated 

 sac, containing the eggs w^hich she is ready to lay. The 

 head presents, first, two reticulated eyes, apart, situated at the 

 extremity of two flexible peduncles, formed by lateral ex- 

 tensions of the head. Second, two antennse, at the least, 

 frontal, scarcely longer than the head, slender, filiform, and 

 composed of very small articulations. Third, two projections 

 underneath these antennae, sometimes in the form of horns, and 

 having a single articulation, sometimes digitiform, (the first 

 finger of the hands, according to Prevost) and of two articula- 

 tions. Fourth, a lower mouth, composed of two sorts of den- 

 ticulated mandibles, without palpi, and of some other pieces. 

 We presume that these projections in the form of horns, are 

 only an appendage, or division of the frontal antennae, but in- 

 creased in size and altered in shape in the males. The two other 

 antennae may be wanting or obliterated in the females, and form 

 in the other sex of one of the species {Chirocepltale cUaphane, 

 Prevost), those singular tentacula, appendaged, and denticu- 

 lated, in the form of a flabby proboscis, capable of being spirally 

 rolled, which Benedict Prevost designates under the name of 

 fingers of the hands. It is probable that the mouth has, as in 

 apus, two pairs ofjaws,a ligula, and a labrum,but the forms and 

 respective situations of which have not yet been well recog- 

 nized. It appears to me indubitable, that this piece, in Xhe 



