176 
the length of the tibiae, second joint twice and a half the length 
of the first, cleft before the middle. 
Intermediate legs : femora rather more than three-fourths the 
length of the tibiae and tarsi taken together ; tibia? about five- 
sixths the length of the femora ; tarsi (pi. xxvii., fig. 7) more 
than three-fifths the length of the tibia?, first joint more than 
three times the length of the second. 
Hind legs : femora about one-third longer than the tibia? and 
tarsi taken together ; tibia? scarcely more than three times the 
length of the tarsi ; tarsi cleft at two-thirds of their length. 
Abdomen : second to fifth ventral segments narrow, parallel, 
of equal length, the first and sixth equally long, together equal to 
the remaining four. 
Genital segments (pi. xxvii., figs. 9-10) : first beneath about 
equal in length to preceding ventral segments taken together ; 
second with horns reaching to two-thirds the length of the third, 
their apical half microscopically tubercular ; third (pi. xxvii., 
fig. 10) above scarcely wider than long, with prominent lateral 
angles. 
Female . Considerably larger than the male, agreeing with it 
in color and markings. Legs proportionately longer than in male. 
Abdomen : ventral segments narrow, parallel, gradually 
increasing in length successively. 
Genital segments : first beneath shorter than the preceding 
ventral segments taken together, the posterior margin concave \ 
lamella? of the second overlapping. 
Ohs. Closely resembling Halobates Hay anus , White (Voy. 
H.M.S. Chalk, xix., p. 52, pi. i., tig. 8, 1883), described from the 
Red Sea. Differs principally in its larger size, the relative 
lengths of the joints of the antenna? and legs, and the shape of 
the terminal genital segment, and less prominently in some minor 
points of coloration. 
I have much pleasure in dedicating this species to my 
esteemed colleague, Mr. Thos. Whitelegge, F.R.M.S., who first 
drew my attention to its occurrence at Tarban Creek, 
Parramatta River, during the course of his investigations in 
regard to the late organic discoloration of the waters of Port 
Jackson. But I must not omit to mention that I have subsequently 
ascertained, through the instrumentality of Mr. Geo. Masters, 
the Curator of the Macleay Museum, that several specimens 
of the larva of this insect, labelled N.S.W., have for many 
years existed under a MS. name in the Collection of the late 
W. S. Macleay. Mr. Masters also collected a few specimens 
many years since upon our coast. As far as I am aware 
the species is confined to Port Jackson, and like its congener, 
H . Hay anus , White, occurs in large u schools ” close to the 
shore, usually in sheltered spots. At first sight I concluded 
that this species was no other than II. Hayanus , which supposi- 
