BRANCHIOPODA. 139 



tremity. Its upper surface is divided by a transverse line forming 

 two united arcs, in two areas, the anterior nearly semilunar, corres- 

 ponding to the head, and the posterior to the thorax. In the middle 

 of the first, we observe three closely approximated simple eyes, or 

 without apparent facets, the two anterior of which are largest and 

 almost reniform, and the posterior much smaller and oval. A du- 

 plicature of the anterior portion of the shell forms a sort of frontal, 

 flattened, semilunar shield beneath, which serves as a base to the 

 labrum. The posterior area, that which corresponds to the thorax, 

 is carinated throughout the middle of its length. This shell is only 

 adherent by its anterior extremity, so that looking from this point 

 we can discover the whole back of the animal. Each side of the 

 shell, seen from beneath and in a strong light, presents a large spot, 

 formed by numerous lines describing concentric ovals, which appear 

 to be tubular and filled with a red fluid. Directly under the shield or 

 frontal disk, we find the antennae and mouth. The former, two in 

 number, are inserted on each side of the mandibles, are very short 

 and filiform, and are composed of two nearly equal joints. The 

 mouth consists of a square, projecting labrum; of two strong, horny, 

 inferiorly inflated mandibles, compressed and dentated at the extre- 

 mity and without palpi; of a large and profoundly emarginated li- 

 gula; and of two pairs of foliaceous jaws laid on each other, the 

 superior of which are spinous and ciliated along the inner margin, 

 and the inferior almost membranous and similar to small false feet; 

 they are terminated by a slender, elongated joint, and are prolonged 

 externally from their base into a species of auricle, (oreillette) fur- 

 nished with a uniarticulated and ciliated appendage, which may be 

 considered as a kind of palpus. According to Savigny(l), the li- 

 gula exhibits a ciliated canal, which leads directly to the oesophagus. 

 The feet, which amount to about one hundred and twenty, insensibly 

 diminish in size, commencing from the second pair; they are all 

 strongly compressed, foliaceous, and are composed of three joints, 

 exclusive of the two long threads at the extremity of the two ante- 

 rior feet, and the two leaflets at the end of the following ones, parts, 

 which, when united, we may consider as constituting a fourth, for- 

 ceps-like joint, or one with two elongated toes converted into a sort 

 of antenniform threads. On the posterior side of the first joint is 

 inserted a large, branchial, triangular membrane; the second also, 

 on the same side, has a red, vesicular and oval sac. On the oppo- 

 site margin of these feet are four triangular and ciliated leaflets, the 

 superior of which is closely approximated to the toes of the forceps, 



(1) Mem. sur les Anim. sans Verteb., Savig 1 ., part I, fasc. I. 



