a» FRESHWATER ENT05I0STRACA OP IT.S.W. 1. CLADOCERA, 



pace is marked by numerous eoneentrie lines of growth caused by imperfect 

 moulting. Free edges of the valves fringed with long ciliated setae. Head 

 small, terminating in a sharp corner anteriorly. Eye distant from the front, 

 ocellus much smaller than the eye, situated close to it. Antennules long and 

 narroAv. Antennae very powerful, more elongated than is usual for the genus, 

 setae, very long and not ciliated. Post-abdomen large, plate-like, dorsal edge 

 sinuated above the middle, bearing small marginal denticles, pre-anal portion 

 also bearing 5-8 lateral spines and the post-anal 4-8 spines; end-claws long, with 

 two small hair-like denticles at the base. Colour orange. Length up to 1.5 mm. 



Male. Eye comparatively larger than in the female. Antennules dilated in 

 the middle, bearing a slender bristle. This species can swim, but usually drags 

 itself along the mud. 



Distribution. — N.S.W. : Centennial Park, University Pond, Lane Cove, Ken- 

 dall, Casino; Queensland, Sumatra, Celebes, India. Ceylon, East Africa, North 

 and South America. 



Ilyocryptus sordidus (Lievin). 



First described by Lievin {1848, p. 34) as Acanthocercus sordidus. Sars 

 recorded its presence in New South Wales in 1896 (Plate 5, figs. 1-3). 



Female. Carapace, seen laterally, like a rounded triangle expanding pos- 

 teriorly; posterior and ventral margins of equal length, passing into each other 

 by a very strong curvature, margins fringed with ciliated setae; dorsal margin 

 very slightly arched. Head comparatively small, seen laterally, triangular in 

 form, fornix prominent. Eye distant from the front, ocellus smaller than the 

 eye and situated near the base of the antennule. Antennules with the proximal 

 joint very small, distal long and slender. Antennae short and thick, not nearly 

 as powerful as in the preceding species. Post-abdomen large, conically produced 

 at the tip, bearing a marginal row of small denticles, 10-14 pre-anal spines, 8-10 

 post-anal; end-claws long and slender, eacli with two secondary denticles. Colour 

 red. Leng-th 1 mm. 



Male. Much smaller than the female, only attaining a leng-th of .4 mm. 

 This species appears to be devoid of swimming powers. 



Distribution. — N.S.W. : Ponds off Botany Rd. and Bourkc St., Maroubra. It 

 occurs in Victoria, Sumatra, China, South Africa, North and South America, 

 Europe. Of world-wide occurrence, it is much rarer in New South Wales than 

 I. spinifer. 



Family CHYDOPtlDAE (Lynaeidae) . 



Fornices extended, uniting with the rostrum to form a beak. Antennae with 

 both rami three segmented. Five to six equidistant pairs of feet. One or two 

 sunnner eggs. Intestine convoluted. 



Kiey to genera of Chydoridae. 



A. Head crested 



B. Post-abdomen bearing marginal denticles Camptocercus. 



BB. Marginal denticles absent '.. .Acroperus. 



AA. Head not crested. 



B. End-claws of post-abdomen with one basal spine. 

 C. Carapace compressed. 

 D. Rostrum pointed. 



E. Anal denticles minute Alonella (most species), 



EE stout Aloua. 



