176 



the length of the tibia^, second joint twice and a half the length 

 of the first, cleft before the middle. 



Intermediate legs : femora rather more tlian three-fourths the 

 length of the tibiae and tarsi taken together ; tibiae about tive- 

 sixtlis the lengtli of the femora ; tarsi (pi. xxvii., fig. 7) more 

 than three-fifths the length of the tibise, first joint more than 

 three times the length of the second. 



Hind legs : femora about one-third longer than the tibiae and 

 tarsi taken together ; tibia^ scarcely more than tliree 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 si.xth 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., 

 tig. 10) above scarcely wider than long, with prominent lateral 

 angles. 



Female. Considerably lai'ger than tlie male, agreeing with it 

 in color and markings. Legs proportionately longer than in male. 



Abdomen : ventral segments narrow, parallel, gradually 

 increasing in lengtli successively. 



Genital segments : first beneath shorter than the preceding 

 ventral segments taken together, the posterior margin concave ; 

 lamellai of the second overlapping. 



Obs. Closely resembling Halobates HayaiMS, Wliite (Voy. 

 H.M.S. Chalk, xix., p. 52, pi. i., fig. 8, 1883), described from the 

 Red Sea. Diflei's principally in its larger size, the relative 

 lengths of the joints of the antennae 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 ISlacleay Mu.seum, 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. Hayanus, White, occurs in large " schools " close to the 

 shore, usually in sheltered spots. At first sight I concluded 

 that this species was no other than //. llayanus, which supposi- 



