BRANCHIOPODA. 253 



l>y tin- cimvnt formed by the action of their feet, which 

 directs theii -ordinary aliment to wards their mouth. They use the hooks 

 which terminate the extremity of their tail to clean their branchiae. 



Daphnia pulex ; Monoculu* pulvx, L. ; Pulex aquaticus arbo- 

 rescens, Swamm., Bib. Nat., xxxi; Perroquet d'eau, Geoff., 

 Hist. Ins. 11,455; Schscf., Die Grim., arm.. Polyp., 1755, 1, 1,8; 

 Straus, Mem. du Mus. d'Hist. Nat. V, xxix, 1 20; Jurine, 

 Mon., viii xi. According to Straus, this species has a large 

 convex ro.-tnnn ; sctir of the oars plumose; first tubercle of the 

 sixth segment linguiform ; inferior edge of the valves dentated ; 

 valvo terminated by a short tail, which is obtuse in the females. 

 This last character distinguishes it from another species with 

 which it has been confounded, the 



Daph. longispina, Str. Deg. Insect. VII, xxvii, 1 1. The 

 female is four millimetres in length *. 

 The last subgenus of the Lophyropa is 



LYNCEUS, Mull. CHILODORUS, Leach. 



It can scarcely be distinguished from the preceding except by the 

 oars, evidently shorter than the shell, the inferior portion of whicli 

 h.i> 1'ut little or no projection. According to Straus the articula- 

 tions of the branchiae are more numerous than in the preceding sub- 

 genera. They all have a little spot before their eye which has the 

 appearance of a second one. The rostrum, longer in proportion than 

 that of the Daphniae, is curved and pointed \. 



The second section of the Branchiopoda, that of the PHYLLOPA, is 

 distinguished from the first, as already stated, by the number of feet, 

 which at least amounts to twenty J and by the lamellated or foliaceous 

 form of their joints. There are always two eyes, which are some- 

 timcs pediculated : several of them have also an ocellus. 



They funu two principal groups. 



In the first CERATOPTHALMA, Lat. there are never less than ten 

 pairs of feet, nor more than twenty-two ; the vesicular body at their 

 base is wanting ; the anterior are never much longer than the others, 

 nor ramified. The body is contained in a shell resembling that of a 

 bivalve, or is naked, each thoracic segment bearing a pair of exposed 

 tcet. The eyes are|sometimcs sessile, small, and closely approximated ; 

 at others, and most frequently, they are situated at the extremity of 

 two Mu>veal>le pedicles. The ova are internal or external, and are 

 contained in a sac at the base of the tail. 



Hi iv the eyes arc sessile and immoveable ; the body is invested 



the other species, see Mem. cit. of Straus ; Mull.. Kntom., and Jurine, 

 Hist cles Mon. fam. II, p. 18588, and p. 181, 200. For the I), sima and D. 

 lo*gisi**a, see Rand., Mono.-.. Y-VI1. 



f See Miill.. Kntum., a. It/nc na ; Jurine, Monoc. p. l5l, 158; and Desmar., 

 Consid., 375378. 



t These animals represent among the Crustacea, the Myriapoda of the class of 



IlKCCt". 



