BRITISH HYDRACHNID.E. 211 



Legs. — In the adult the usual number, eight. These legs have 

 six joints. The first joint is small and almost hidden under the 

 epimera. The other five sections of the same leg are nearly of 

 one length. They are covered with a great number of simple 

 hairs. A few of those on the joints are plumose, but are quite 

 without the long swimming-hairs described before. Each tarsi is 

 fitted with two strong claws, which can be retracted at will into 

 the distal end of the tarsus. The first pair of legs are the shortest. 



The epimera is chitinous, with a border of a thicker skin round 

 each epimeral plate, which is fringed with a quantity of fine hairs. 



Eyes, four. On the anterior portion of the dorsal surface is an 

 oblong-shaped piece of chitine, which projects on each side towards 

 the larger end, and it is on the margin of these two projections the 

 eyes are situated (see Fig. 8). 



The mouth-organs are suctorial. The palpus is short, and 

 reaches no further than the sucker-like mouth. It has hairs at the 

 joints (see Fig. lo). 



Distribution. — It is not common. I took two specimens in 

 1893 — one at Woking and one at Sunningdale. In 1894 I took 

 two specimens at The Warren, Folkestone, and one at Redhill. 

 In 1895 I did not take a single specimen. In 1896 I took six 

 specimens at The Warren, Folkestone, and on Sept. the 8th two 

 in North Wales. These last two I have still alive. Seven months 

 since they were captured. I believe both to be females, but they 

 have not deposited any ova. 



Larva and nymph I do not know. The adults are very slug- 

 gish in their movements, and keep well at the bottom of the water, 

 slowly crawling about amongst the debris, 



Linneus had priority in naming this mite, and he gave it the 

 specific name of Aquaticus, and this name was retained by some of 

 the writers that came after him, as will be seen in the bibliography. 

 I also think myself that the name Aquaticus should be kept for 

 that reason. I do not like the alteration of specific names, for 

 the practice leads as a rule to much confusion ; but when we get 

 two such well-known writers on the Hydrachnidce as Koenike and 

 Piersig — both of whom call it holosericea after Latreille — I must 

 submit to their ruling and say no more on that question. 



