BY MARGUERITE HENR?. 561 



Distribution. — This species has not hitherto been recorded from New South 

 Wales; both males and females were abundant in a collection from Holbrook. 

 Sars described it from specimens sent from Victoria. 



Division 2. CYCLOPOIDA. 



Cephalothorax much broader than the abdomen. Articulation occurring be- 

 tween the 4th and 5th free segments. Both antennules transformed in the male. 

 Antennae usually devoid of exopodites. Fifth pair of legs rudimentary. Heart 

 absent. Ova carried in two ovisacs which are attached laterally or sub-dorsally. 

 There is only one free-swimming freshwater family. 



Family CYCLOPIDAE. 



Antennules composed of a varying number of segments, never exceeding 

 seventeen. Antennae four-segmented, with an elongated seta at the end of the 

 first segment. Natatory less well developed, last pair of legs small and alike 

 in the two sexes. 



All the freshwater forms included in this fimiily are classed by most authors 

 in the one genus Cyclops. This genus, however, comprises so many species that 

 several attempts have been made to separate them into groups. Sars in his Crus- 

 tacea of Norway (1913) has gone further than this and has divided the old genus 

 Cyclops into five genera; this classification appears to be a natural one and has 

 been followed in this work. 



Key to genera of the Cyelopidae. 



A, oth- pair of legs composed of two segmentp. 



B . Distal segment armed only with setae Mesocyclops. 



BB. Distal segment armed with setae and spines. 



C. One lateral spine Cyclops. 



CC. Two spines Pachycyclops. 



AA. 5th pair of legs composed of a trilobate lamella. 



B. Lamella armed with one seta and one spine Leptocyclops. 



BB. Lamella armed with two setae and a spine or three spines. 



Platycyclops. 



Genus Cyclops Muller, 1776. (As restricted by G. 0. Sars.) 



Lateral parts of the three anterior segments of the cephalothorax well de- 

 fined, last segment produced laterally. Abdomen slender, with the genital seg- 

 ment of the female dilated in front. Antennules of varying length, strongly 

 hinged in the male. Antennae with all four segments well defined. Rudimentary 

 palp of the mandibles with two long, plumose setae and a short bristle. Nata- 

 tory leg's with both rami composed of three segTuents, sometimes only two, endo- 

 podites of the fourth pair with two apical spines. Fifth pair very small, com- 

 posed of two segments, distal segment not expanded and provided with an apical 

 seta and a lateral spine. Seminal receptacle usually oval in shape. 



Two species are known in New South Wales. 



Key to species of Cyclops. 



A. All natatory legs with both rami two segmented varieans. 



AA. 1st pair with both rami two-segmented, remaining pairs with both rami three- 

 segmented australis. 



