REPORT ON THE PELAGIC HE.MIPTERA. 63 



deep narrow furrow, anteriorly fork(?d, the upper branch nearly perpendicular, but slopiut: 

 slightly forwards ; the lower and shorter branch horizontal, and occupied for all or most 

 of its length by the longitudinal opening of the mesothoracic spiracle. On the inner side 

 the acetabulum is bounded by the erect connexivum, which at its commencement has 

 its edge slightly but acutely folded over to the outer side. 



The Coxa is similar to the middle coxa, but rather lono-er. 



The Trochanter is similar to the middle trochanter. 



The Femur is also similar to the middle femur, and nearly as long or longer, but less 

 stout. 



The Tibia is similar to the middle tibia, but without longer hairs on the inner side. 



The Tarsus (PI. II. fig. 5, Ji.t.) is two-jointed, with the second joint cleft and clawed 

 before the apex. 



DESCRIPTIOX OF THE SPECIES. 



In the following pages four species of Halohatodes are described, namely : — 



Halobatodes litwratus, Stal. 

 „ histrio, n. sp. 



,, compa)-, n. sp. 



„ stdli, Dohrn. 



Of these the first three are before me, and are certainly congeneric. The fourth, which 

 was described as Halobates stali, I have not seen, and as the original deserijjtiou does 

 not give any of the details of structure, it is perhaps not rightly located in this genus. 

 From the description of the coloration, however, it seems to be probably a Halobatodes. 



Key to the Species. 



Owing to insufficiency of material, colour differences have to be employed in the following key 

 (as well as in the diagnoses of the species) more than structural differences. 



1. Ground colour yellow testaceous ; markings black or brownish-black, . . 2 

 Ground colour dull black ; markings yellow testaceous, .... 3 



2. The central longitudinal black line of the thorax continued to the abdomen, littiratits. 

 The central longitudinal black line of the thorax not reaching the abdomen, . Jmtrio. 



3. Under side of body dull black, ...... coinpai: 



Under side of body yellow testaceous, ...... stdli. 



