BRANCHIOPODA. 135 



fringe of hairs or bearded threads along the edges; and of an elon- 

 gated tail tapering to a point, consisting of nine segments terminated 

 by two more or less elongated leaflets fringed with cilia. Under its 

 second segment we find the male organs of generation, and in the 

 female an elongated sac containing the ova she is ready to produce. 

 In the head we observe, 1. Two reticulated eyes situated at the ex- 

 tremity of two flexible peduncles formed by lateral prolongations of 

 the head; 2. Two antennae at least, frontal, scarcely longer than the 

 head, slender, filiform and composed of very small joints; 3. Two 

 projections under them, sometimes resembling a uniarticulated horn, 

 and at others digitiform the premier doigt des mains, Bened. Pre- 

 vost and biarticulated; 4. A mouth underneath composed of two 

 kinds of dentated mandibles without palpi, and of some other parts. 

 We suspect that these horn-like projections are merely an appen- 

 dage, larger and differently formed in the males, of the frontal an- 

 tennae; the two other antennae may be wanting or be obliterated in 

 the female, and form in the other sex of one of these species Chiro- 

 cephala diaphana, Prevost those singular appendicated and dentated 

 tentacula, in the form of a soft proboscis which is susceptible of 

 being spirally convoluted, designated by Benedict Prevost under 

 the name of doigts des mains, or fingers. It is probable that, as in 

 Apus, the mouth is furnished with two pairs of jaws, a ligula and 

 a labrum, but their respective form and situation have not yet been 

 well ascertained. I am convinced that the part resembling a ros- 

 trum mentioned by Schaeffer, and which Prevost calls a valve (sou- 

 pape) is the labrum; that the four bodies or tubercles placed on the 

 sides, mentioned by the former, are the mandibles and the two upper 

 jaws; and that the parts considered by the second as cirri (barbillons) 

 are also maxillary. The two first feet, which, according to Schaeffer, 

 are composed of but two joints, the last terminating in a point, would 

 represent the two firstfoot-jaws of the Crustacea Decapoda, and the 

 two large antenniform feet of an Apus(l). The chief of the male 

 organs of generation, at least those which are considered as such, 

 consist in two conoid biarticulated bodies, which only project by 

 pressure (Schaeffer), situated under the second ring, in which vessels 

 terminate that arise from the first. M. Prevost presumes that the 

 two vulvae of the female are placed at the extremity of the tail, but 

 that they afford no issue to the ova. This issue (two apertures ac- 

 cording to Schaeffer), is in the second ring, and communicates in- 

 ternally with the sac containing the eggs, which acts as an external 



(1) See Mem. sur les Anim. sans Verteb., Savign. parti. 



