FRESHWATER CRUSTACEA OP TASMANIA. 81 



Ceriodaphnia planifrons, sp. n. (PI. 15. fig. 17.) 



This small species has the carapace more elongated than C. hakea, and has the 

 posterior angle of the carapace clearly marked and almost forming a distinct spine. 

 The constriction between the thorax and the head is not very clearly marked. The 

 head is not furnished with any spines, and its outline is regularly curved without any 

 distinct sinuosity ; nor is there any spine or turgescence in front of the insertion of the 

 first antenna?. 



The first antennae have short terminal setae, and one rather lon£f seta on a rid^e close 

 to the apex. 



The ocellus is clearly marked. 



The second antennas are similar to those of C. hakea. The anal claws are Ions and 

 unarmed, and there are five lateral spines behind them. These spines nearly reach to a 

 fairly distinct angle, which is not marked in C. hakea. 



Length "9 mm. 



Colour. Green. 



Occurrence. In the plankton of Lake Sorell. No males observed. 



Genus Simocephaltjs (Schcedler). 



Four species have been described from Australia by Sars (Archiv for Math, og 

 Naturvid. vol. xviii. (1896) ; and Forhand. Vidensk. Selsk. Christiania, 1885), agreeing 

 fairly closely with northern members of the genus. The species described below does 

 not offer any marked characters. 



Simocephaltjs dulvertonensis, sp. n. (PI. 15. figs. 5-7.) 



The carapace is rather quadrate in form ; the posterior angle is rounded and dorsal in 

 position, with its margin carrying a few short spines. The ventral margin is uniformly 

 clothed with setae, which towards the posterior end are stout and spiniform. The under 

 surface of the head is greatly elongated, and there is a small projection just in front of 

 the insertion of the first antennas. 



The first antennas have their sides hollowed out ; they carry about ten hollow setae, 

 and a single small seta on a projection about halfway down the stem (PI. 15. fig. 6). 



The second antennae have the structure characteristic of the genus ; the tops of the 

 segments are very distinctly serrated. 



The anal claws are long and without any additional spines at their base. Behind the 

 claws are about eight strong spines, the anterior ones being very small. The angle 

 behind these spines is fairly prominent and carries several rows of small bristles (PI. 15. 

 fig. 7). The hind part of the body between this angle and the two dorsal setae is also 

 slightly angular. 



Length 2 mm. 



Colour. Green. 



Occurrence. Among thick weed in Lake Dulverton. No males. Also among weed 

 in Great Lake. 



