New Crustacea from the Swan River Estuary. 
41 
Male. 
• Length 0-39 mm. The expansion of the basal segment of the fifth 
leg has only two setae and does not extend much beyond the distal segment. 
The distal segment is much more normal than in the female, having four 
stout spine-like setae and one slender seta around the margin. 
Appendages: First antenna has the proximal segments somewhat 
swollen and the distal segments relatively shortened. The aesthetasc is more 
massive than in the female and extends beyond the end of the appendage 
for some distance. 
Colour. — White with a yellowish-green tinge. 
Discussion. 
Some fifteen species of Mesochra are known. The female of M. parva 
is clearly distinguished by the unusual shape and structure of the fifth leg. 
The lack of a spine on the anal operculum and the seta formula serve to 
distinguish it from at least some of the species. Many of the species are 
know n from the female onl\ , so it is impossible to note specific characters 
for the male. 
