HORN EXPEDITION—CRUSTACEA. 
233 
Judging, liowever, from the fact that an investigation of Australian 
specimens of the allied genus Lepidurus procured from New South Wales, 
Victoria, South Australia, Tasmania and New Zealand has revealed the fact that 
they ai’e all referable to the single species Lepidimis viridts and that specimens of 
Apus from Central Australia, South Australia, New South Wales, Victoria and 
West Australia are all referable to the single species Apus australiensis it is most 
probable that this may be safely regarded as the only Australian species of the 
genus. Further than this, we venture to think, after the examination of a large 
collection of Lepidurus hitherto referred to some four species and after seeing 
the great variations existing amongst the members of these, that an examination of 
the species of both the genera from various parts of the world would result in 
materially reducing the number of species. 
For the present, and partly in consequence of its geographical isolation, we 
have thought it advisable to distinguish the Australian Apus specifically. 
Distribution. —Cooper’s Creek and Farina (S. A. Museum), Upper Onkaringa 
Creek (Elder Expedition), Whychogga Lake, Darling River (Nat. Museum, Mel¬ 
bourne), Hunter River, Macquarie River, and Mossgiel, N.S.W. (Aust. IVIuseum, 
Sydney) ; Gunbower Island, Murray River, and Kewell, Victoria (J. A. Kershaw, 
E.sq.); Adminga and Stevenson Creeks, Charlotte Watei's and Alice Springs, 
Central Australia; Coolgardie, West Australia (C. French, Esq.); Hannan, West 
Australia (H. Berry, Esq.). 
The variations in dimensions are of considerable extent. Those of four male 
specimens and eleven females are as follows, the length from the anterior edge of 
the carapace to the posterior end of the carina being taken as the standard 
a 
Males. 
(D 
(2) 
(3) 
(4) 
Length a - b - 
100 
100 
100 
100 
b - c - 
33 
31 
30 
32 
d- e - 
65 
65 
60 
63 
b-f - 
147 
116 
88 
136 
