SOME AUSTRALIAN FRESHWATER COPEPODA AND OSTRACODA. 33 



The antennules are composed of twenty-five segments, 

 some of the proximal ones being very small. When reflexed 

 tbey extend about as far as the middle of the genital 

 segment. 



The antennae (fig. 4) are biramus, the outer branch, com- 

 posed of six segments, is about the same length as the inner. 



The mandibles are strongly built; the masticatory part 

 is expanded and bears eight somewhat rounded denticles; 

 the outermost of these is the largest, and is separated from 

 the others by a sinus. 



The maxillae and anterior maxillipedes are of normal 

 structure. 



The posterior maxillipedes (fig. 5) are long and slender, 

 the four distal segments are small and bear numerous setae. 



The first four pairs of natatory legs are long and slender, 

 each ramus consisting of three segments; the inner rami 

 are shorter than the outer. In addition to the setae, the 

 outer ramus of each leg bears a denticulated spine on the 

 outer edge of each segment, the third segment also bears 

 two terminal spines, one of which is very long and coarsely 

 denticulated. The basal segment of each leg of the fourth 

 pair (fig. 2), bears a long curved spine on the inner edge, 

 which reaches as far as the end of the middle segment of 

 the inner ramus. The fifth pair of legs (fig. 3) is slightly 

 shorter; the outer ramus is armed like the preceding ones, 

 but bears in addition a long curved spine on the inner edge 

 of the middle segment. 



The ovisac is rounded, and is situated on the ventral 

 surface, 



The male is smaller than the female, the abdomen is 

 very slender, and consists of five segments. The right 

 antennule (fig. 6) is modified, being swollen and hinged. It 

 may be divided into three sections; the first consists of 



C— July 2, 1919. 



