103 Mr. F. Ralfour-Browne on the 



fication ( x 600), it will be seen that the two differ from one 

 another in one respect. The anterior or inner claw is smooth 

 on its concave side, while the other bears two or more teeth 

 in two series side by side. At first I thought that the 

 number o£ teeth in these series was g"oing to give anotiier 

 definite specific character, but either they break off very 

 readily or else the number varies within the species. I 

 imagine, however, that H. nomax (including its var. broione- 

 anus, which even in this character agrees with it) has usually 

 longer and more distinct teeth in each series than the otliers, 

 there being either three or four on each side. 



2. The Median Tarsi. 



The form of tlie basal segment of the median tarsus varies 

 somewhat in the different species, but it is of use for separating 

 off H. immaculatus and nomax from the others, since in these 

 two species the posterior edge is markedly concave or excised 

 instead of being practically straight. The excision is much 

 more marked in nomax than in immaculatus, but any con- 

 fusion there might be between these two species on this 

 character is avoided by reference to the anterior tarsal claws. 



3. The ^deogus and its External or Accessory Lobes. 



Edwards is the only author who has used the form of the 

 sedeagus as a specific character, but he failed to make full 

 use of his discovery. The sedeagus with its accessory lobes 

 readily separates all our British species, and it also makes it 

 quite clear that H.furcatus of Seidlitz is a good species, and 

 not a mere variety of H.fuhkollis of Eiichson. 



The sedeagophore in the Haliplids is a very peculiar struc- 

 ture, and, although in the different species the form differs 

 considerably, all the forms are built upon one type, as is, of 

 course, to be expected within a genus. Sharp (19) gives a 

 drawing and short description of the sedeagophore of Tl.falvus, 

 F., but this happens to be one of the simpler types, and 1 

 will therefore give a general description of the structure with 

 the aid of a diagram. 



The sedeagophore consists of the sedeagus — or penis, as it 

 used to be called — -and two side-lobes, and the whole apparatus 

 is bilaterally asymmetrical and flattened from side to side. 

 The two side-lobes, external or accessory lobes, differ from 

 one another, one being, as Edwards describes it, " merely a 

 concave scale, usually oblong or subtriangular, with a 

 rounded apex.'''' The shape of this *' scale " varies somewhat 



