54 CRUSTACEA BRANCHIOPODA CHAP, n 



claws of telson with two accessory teeth (includes sub-genera 

 Alonella, Pleuroxus, Peracantha). 

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



Leach : compound eye present. Monopsilus, Sars : 



compound eye absent. 



Tribe II. GYMNOMERA, 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 limbs, 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. Leptodora hyalina, x 6. Lake Bassenthwaite. A.I, First antenna ; 

 Car, carapace ; I, VI, first :nd 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," Terme's Fiizetek, xxv., 1902, p. 

 201 ; for Paraguay, Bibliotheca Zoologica, Heft 44 ; for Ceylon, Terme's Fiizetek, 

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

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

 3, and xix., 1897, No. 1. G. W. S. 



