1888.] AUSTRALIAN CLADOCERA. 43 



out considerably in front; in the middle part however, they are 

 nearly straight and posteriorly ascend a little towards the rounded 

 infero-posteal corners. The posterior part of the carapace is 

 narrowly truncate, with the edges somewhat obliquely rounded. 

 Viewed dorsally or ventrally (fig. 2), the carapace exhibits a 

 regular obovate form, the sides evenly arched and the posterior 

 part tapering to an obtuse point. The head, owing to the greatly 

 developed fornices, is in the latter aspect very broad, scarcely 

 narrower than the carapace, and clypeiform. Viewed laterally 

 (fig. 1), it appears much narrower, with the. edge of the fornix 

 somewhat flexuous and separated from the anterior edges of the 

 valves by a deep and rather narrow incision, from the bottom 

 of which the antennae are seen to project. It is, as in CJu/<hnt? 

 and Pleuroms, somewhat movable in relation to the carapace 

 and rather decumbent, terminating in an acute, slightly curved 

 rostrum, that does not however project beyond the inferior edges 

 of the valves. 



The shell appears quite smooth, without any distinct sculp- 

 turing, save the usual minute punctation, and has the inferior 

 edges of the valves fringed with a dense series of very delicate 

 finely ciliated setae (see fig. 4), and, besides, armed at a short 

 distance from the infero-posteal corners with a single rather 

 strong denticle. On viewing the animal from below (fig. 2), 

 these edges invariably appear wide apart in the middle, and 

 limit a rather large oblong opening leading to the inner cavity 

 of the shell. 



The eye, located near the dorsal edge of the head and at a 

 somewhat considerable distance from the rostrum, is cf larger size 

 than usual in this family, having too 4 very large and conspi- 

 cuous crystalline lenses, projecting anteriorly from the dark 

 blackish ocular pigment. 



The ocellus is much smaller than the eye, scarcely more 

 tlian i/4 as large, and of an irregular quadrangular form; it 

 is ^located somewhat nearer to the eye than to the tip of the 



The antennulae, originating beneath the base of the rostrum, 



