BnANCHIOPODA. 253 



carried along by the current formed by the action of their feet, which 



directs their ordinary aliment towards their mouth. They use the hooks 



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



Daphnia pulex ; Monoculus pulex, L. ; Pulex aquaticus arbo- 



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



Hist. Ins. II, 455; Sch^f., Die Griin., arm., Polyp., 1755, 1, 1, 8; 



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



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



convex rostrum ; setae of the oars plumose ; first tubercle of the 



sixth segment linguiform ; inferior edge of the valves dentated ; 



valves terminated by a short tail, Avhich 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 — 4. The 

 female is four millimetres in length ♦. 

 The last subgenus of the Lophyropa is 



Lynceus, Miill. — Chilodorus, Leach. 



It can scarcely be distinguished from the preceding except by the 

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

 has but 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 lias the 

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

 that of the Daphniee, is curved and pointed f . 



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- 

 times pediculated : several of them have also an ocellus. 



They form 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 

 feet. The eyes are!sometimes sessile, small, and closely approximated ; 

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

 two moveable pedicles. The ova are internal or external, and are 

 contained in a sac at the base of the tail. 



Here the eyes are sessile and immoveable ; the body is invested 



* For the other species, see Mem. cit. of Straus ; Miill., Entom"., and Jurine, 

 Hist, des Mod. fam. II, p. 185—88, and p. 181, 200. For the D. sima Rud D. 

 longispina, see Rand., Monoc, V-VII. 



t See Mull., Entom., G. lynceus ; Jurine, Monoc. p. l5l, 158; and Desmar., 

 Consid., 375—378. 



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

 Insects. 



