BY MARGUERITE HENRY. 47 



Chydorus leonabdi King. 

 {Syn. C. minor Lilljeborg, C. elelandi Henry). 



First described by King in 1852 (p. 258). Figured by Sars in 1896 (Plate 

 v., flgs. 4-5). ' 



Female. Carapace rounded, doi-sal and ventral margins strongly arched, pos- 

 terior very short. Head somewhat depressed, rostrum long and jsointed. Eye of 

 moderate size, ocellus slightly smaller, situated nearer the eye than the rostral tip. 

 Carapace devoid of sculpturing, ventral margin fringed with bristles. Anten- 

 nules short, olfactory setae terminal. Post-abdomen comparatively wide, supra- 

 anal angle prominent, 8-10 anal denticles, end-claws each with two basal spines. 

 Length .25 mm. 



This species is regarded by some authors as identical with C. sphaericus 

 Muller. It is undoubtedly nearly related to this species and should perhaps be 

 classed as a variety. A larger form described as C. elelandi attains a length of 

 over .3 mm., has a pitted carapace, and 12 anal denticles, but in other respects 

 is identical with C. Isonardi. 



Distribution. — Widely distributed in N.S.W. : St. Leonards, Denham. Court, 

 Waterloo Swamps, Botany, Kendall, Lett River, Holbrook, Cumbalum. It also 

 occurs in Europe, Africa, Ceylon, Singapore and South America. 



Chydorus ovalis Kurz. 



Described in 1874 (p. 79, Plate iii., fig. 2). 



Female. Carapace, seen laterally, evenly rounded, posterior part depressed, 

 posterior edges very short. Head not depressed, terminating in a long pointed 

 rostrum. Eye larger than the ocellus, which is nearer to it than to the tip of the 

 i-ostrum. Antennules short and thick, scarcely reaching the middle of the rostrum, 

 one olfactory seta situated laterally, the others terminal. Post-abdomen short 

 and broad, supra-anal angle projecting, pointed. Twelve to fifteen anal denticles; 

 end-claws moderately large, with two unequal basal spines. Colour yellowish 

 brown. Length .6 mm. 



Distribution. — N.S.W. : Centennial Park. Europe, North America. 



Genus A l o n e l l a Sars, 1862. 



Head not eai-inate. Valves of the caxapace reticulate or striated. Rostrum 

 variable. Infero-posteal angle toothed or smooth. Antennae with 8 swim m ing 

 hairs. 5 pairs of leg's. Post-abdomien large, pre-anal angle usually not pro- 

 minent, lateral spines usually ahsent, end-claws with one or two basal spines. 



This is a somewhat unsatisfactory genus, consisting of forms that are not 

 easily separable and yet differ widely in many points. Some of the speci-es 

 approach the genus Alona and others Pleuroxus. About twenty different species 

 have been described, four of which occur in New South Wales. 



Keti to species of Alonella. 



A. Claws with one basal spine. 



B. Post-abdomen armed with marginal and lateral denticles. 



C. Valves striated karua. 



CC. Valves reticulated. 



D. Margin of lip-plate notched duoodonta. 



DD. Margin of lip-plate entire clathratula. 



BB. Post-abdomen with marginal denticles only diaphana. 



AA. Claws with two basal spines excisa. 



