46 FRESHWATER EXTOMOSTEACA OF X.S.W. i. CLADOCEEA, 



Chydorus unispinus, n.sp. (Plate vii., figs. 4-4a.). 



Female. Carapace, seen laterally, broadly oval; doi-sal margin strongly 

 arched, ventral also curved, bulging somewhat anteriorly, posterior edges short, 

 slightly curved. Infero-posteal corner armed with a short backwardly-direetea 

 spine. Head of moderate size, terminating in a produced, acutely-pointed ros- 

 trum. Eye of moderate size, ocellus smaller, situated slightly closer to the eye 

 than to the tip of the rostrum. Antennules short, not nearly reaching the tip of 

 the rostrum. Lip-plate long, the margin smooth. Post-abdomen strongly built, 

 anal sinus very distinct; end-claws long, curved, each armed with two unequal- 

 sized basal spines, 12-15 groups of anal denticles. Colour pale yellow. 



This species resembles the barroisi group in that it has a spine ou the 

 infero-posteal corner; it differs from all the other members of the group, how- 

 ever, by the lip-plate having a perfectly smooth margin and in the curious arma- 

 ture of the post-abdomen. 



Distribution. — N.S.W. : Botany. 



Chydorus globosus Baird. (Plate vii., fig-s. 6-6a.). 

 {Syn. Chydorus augustus King). 



First described by Baird in 1850 (p. 127). 



Female. Form almost spherical, without carapace angles. Dorsal and ven- 

 tral margins strongly arched, posterior edges short. Carapace smooth or reticu- 

 lated. Head comparatively large, rostrum produced, acute. Eye large, ocellus 

 much smaller than the eye and situated slightly nearer to it than to the tip of 

 the rostrum. Antennules very short and thick. Post-abdomen long and slender,, 

 of uniform breadth throughout, supra-anal angle very small; numerous anal den- 

 ticles present; end-claws armed with a series of secondary spinules which be- 

 come hair-like towatds the tip, two basal spines of unequal length. Colour vary- 

 ing from yellow to dark brown. Length .8-. 9 mm. 



Distribution. — This large form is very widely distributed in New South. 

 "Wales : Centennial Park,_ Botany, Sydney University, Five Dock, Corowa, Banga- 

 low, Lett River. It also occurs in Victoria, India, Europe and North America. 



Chydorus jugosus, n.sp. (Plate vii., figs. 5-5a.). 



Female. Carapace, seen laterally, rounded in outline, dorsal margin very 

 strongly arched, ventral evenly curved, posterior edges very short and almost 

 straight; infero-posteal corner unarmed. Head of moderate size, rostrum pro- 

 duced, acutely-pointed. Eye large; ocellus very slightly smaller, irregular in 

 shape and situated much closer to the eye than to the tip of the rostrum. ' An- 

 tennules tapering at the ends, olfactory setae comparatively long, reaching more 

 than half the length of the rostrum. Lip-plate large, the backwardly-directed 

 portion narrowly produced. Ventral margins thickly fringed with long feathered 

 bristles. Surface of the carapace very conspicuously marked with an oblique, 

 rarely branching series of ridges which give the appearance of alternating light 

 and dark bands. Post-abdomen very strongly built; end-claws long, slightly 

 curved, each with two basal spines which are both comparatively long though 

 unequal; 14-16 anal denticles with small spinules between them. Colour brown.. 

 Length .74 mm. 



Distribution. — N.S.W. : Holbrook. 



Chydorus denticulatus Henry. 

 Proc. Roy. Soc. N.S.W., lii., 1918 (1919), p. 480, PL slii., figs. 15, IC. 

 Distribution. — N.S.W. : Centennial Park, Sydney University Pond. 



