54 CRUSTACEA — BRANCHIOPODA chap, ii 



claws of telson with ttoo accessory teeth (inchides sub-genera 

 Alonella, Pleiiroxus, Peracantha). 

 B. Body small, spheroidal ; the head depressed. Ghydorus, 



Leach : compound eye present. Monopsilus, Sars : 



compound eye absent. 



Ti'ibe II. Gyjinomera, Sars. — The carapace forms a closed brood-pouch, 

 which does not cover the body ; all the thoracic limbs prehensile. 



Fam. 7. Polyphemidae : four pairs of thoracic hmbs, provided with a 

 gnathobase. 



Fresh-water genera. — Polyphemus, Miiller, with no rudimentary 

 exites on first three thoracic limbs. Bythotrephes, Leydig (Fig. 

 13), with no trace of processes on the outer sides of the limbs. 

 Marine genera. — Evadne, Loven, the head not separated by a, 

 constriction from the thorax. Podon, Loven, with deep 

 cervical constriction. 



Fig. 24. — Leptodorahyalina, x 6. Lake Ba.ssenthvvaite. A.l, First antenna ; 

 Car, carapace ; I, VI, first and sixth thoracic appendages. 



Fam. 8. Leptodoridae : six pairs of thoracic limbs, with no gnathobase. 

 Only genus, Leptodora, Lilljeborg (Fig. 24), from fresh water. 



Note. — For extra -European Cladocera consult Daday, " Microskopische 

 Siisswassertiere aus Patagonien und Chili," Termes Fiir.etek, xxv., 1902, p. 

 201 ; for Paraguay, Bihliotheca Zoologica, Heft 44 ; for Ceylon, Termes Fuzetek, 

 xxi., 1898; and for Australia, Sars, Christiania Vidensh. Forhand. 1885, 

 No. 8, and 1888, No. 7 ; and Arch. /. Math, og Naturvid. xviii., 1896, No. 

 3, and xix., 1897, No, 1.— G. W. S. 



