TACHIDIUS. 21 



with rather long hairs, some of which are plumed with 

 strong spine-like seta3 ; in the male the fifth and sixth 

 joints form a large vesiculiform swelling (fig. 3), the 

 last joint forming a strong claw ; a curved spine is 

 also attached to the outer margin of the swollen joint 

 (fig. 3 a). Posterior antennae 2-jointed, the secondary 

 branch (fig. 5) small, 1- jointed. In the male the 

 inner branch of the second pair of feet (fig. 11) has its 

 marginal setae much reduced in size, and the second 

 joint has attached to its apex a strong spine which is 

 nearly as broad and quite as long as the much nar- 

 rowed terminal joint ; the outer branch of the third pair 

 has also very small marginal seta and is armed at its 

 extremity with three strong spines (fig. 12), one of 

 which is very long. Fifth pair of feet in both sexes 

 broad, subquadrate, single-jointed, much larger in the 

 female (fig. 13) than in the male (fig. 14), and bearing 

 several marginal setae, some of which are plumose. 

 The innermost of the two principal tail setae is much 

 the longest, and both are finely aculeate throughout 

 (fig. 16). The first abdominal segment bears on its 

 outer angles (fig. 15) two spines. Eye small, situated 

 near the base of the anterior antenna. Colour grey 

 or yellowish brown. Length -^th of an inch ('65 mm.). 

 There are probably few brackish marsh-pools in 

 which Tachidius brevicornis may not at times be found, 

 more especially in the autumn months, when long- 

 continued warmth has developed many successive 

 broods of these rapidly multiplying tribes. In pools 

 of this kind I have found it often in great abundance, 

 the following being some of the localities of which I 



