SOME AUSTRALIAN FRESHWATER COPEPODA AND OSTRACODA. 37 



The caudal setse are of different lengths instead of being 

 equal. 



The spine on the basal segment of the fourth leg in the 

 female bears a row of denticles instead of being smooth. 

 The fifth pair of legs in the male differs in the number of 

 segments in the rami and in the armature. 



Specific Characters. — Female. Body slender with the 

 cephalothorax oval in shape, narrowed in front and behind; 

 lateral parts of the last pedigerous segment rounded. 

 Abdomen composed of four segments, of which the genital 

 segment is the largest.- Antennule composed of twenty- 

 five segments, only reaching as far as the base of the 

 cephalothorax. Fourth pair of legs each with a long denti- 

 culated spine on the basal segment. Last pair of legs with 

 the curved process of the outer ramus large and coarsely 

 denticulated, inner ramus reaching beyond the middle 

 segment of the outer ramus. 



Male smaller than the female, abdomen slender, composed 

 of five segments. Right antennule bearing three or four 

 sensory processes, swollen. Last pair of legs short and 

 stout; right leg with a terminal spine on the tri-articulate 

 outer ramus, one lateral spine on each of the other seg- 

 ments, inner ramus small, composed of one segment bear- 

 ing a terminal spine; outer ramus of the left leg with two 

 broad segments, terminal segment bearing four short spines 

 und a longer lateral spine ; inner ramus small, one seg- 

 mented, bearing four short spines. 



Collected at Cumbalum in January. Type specimen in 

 the Australian Museum, No. P 4338. 



Family DIAPTOMIDiE. 



Genus DIAJJOMUS, Westwood. 



Diatomus orientalis, Brady. 



This species was first described by Brady in " Notes on 



Entomostraca collected in Ceylon," Linn. Soc. Jour. Zool., 



f 



