ON SOME AUSTRALIAN CLADOCERA. 471 
ACROPERUS SINUATUS Sp. 0. 
(Plate XL, figs. 5, 6.) 
The length of the adult female reaches 0°59 mm. The 
carapace is compressed; seen from the side, its shape is 
truncated oval. The dorsal margin is only slightly arched; 
the ventral edges of the valves are straight for the greater 
part of their length and form an abrupt angle with the 
anterior free edges. The posterior edges are sinuated, 
forming an obtuse angle with the ventral edge, convex 
about the middle, concave dorsally, meeting the dorsal 
margin at almost aright angle. There are no denticles 
present on the postero-ventral angle. 
The head is rather large; the dorsal margin forms an 
even curve, continuous with that of the carapace. The 
anterior contour of the head is almost vertical. Inferiorly 
the head terminates in a very blunt rostrum pointing 
downwards. ‘The sculpture of the carapace consists of 
distinct, oblique striations. 
The eye is large, with conspicuous crystalline lenses; the 
ocellus is smaller and situated slightly nearer to the tip of 
the rostrum than to the eye. 
The antennules are long and reach beyond the tip of the 
rostrum; each bears a tuft of sensitive bristles at the apex. 
The tail-piece (fig. 6) is more slender than in the fore- 
going species, and the supra-anal angle is not so distinct, 
but the armature closely resembles it, there being eleven 
lateral bundles of spines present; the end-claws are long, 
each bearing two denticles, one at the base and the other 
about the middle of its length; a row of spinelets is present 
between the two denticles. 
There may be two summer eggs present in the brood 
pouch, one in front of the other. 
