C. D. SOAR ON THE GENUS HYDRACHNA. 277 



skin. There are no papillae visible. The specimen described by 

 Dr. Koenike was a male measuring about 3*5 mm. My own 

 specimen was a female measuring about 5*0 mm., of a bright 

 red colour with a pale patch on the dorsal surface. I had only 

 one specimen, which was sent me from the Norfolk Broads by 

 Mr. Browne. This is the first time this species is recorded as 

 British. It is not necessary to give a figure, the smooth skin 

 being quite sufficient for identification. 



2. Hydrachna geographica, Mull. 



There is no difficulty in recognising this mite. It is larger 

 in the adult stage than any other species amongst the 

 Hydrachnidae. The females in some cases measure as much as 

 8 mm. in length and the males 6 mm. In addition to this the 

 colour is symmetrically arranged in masses of black and red. 

 I have not seen an adult, but I once took in Epping Forest 

 three nymphs from a small pond at Snaresbrook. These were 

 of a very large size. I have visited the same pond many times 

 since, but have failed to find any more specimens. I have found 

 this species mentioned as very common round London, but up to 

 the present I have failed to find it except where mentioned 

 above. Recorded in Science Gossip. 



3. Hydrachna paludosa, Thon. 



The entire mite is of a red colour. Male about 2 6 mm. in 

 length. It is a well-niarked mite, the plate behind the eyes 

 being deeply bayed in from the posterior margin (Plate 21, 

 Fig. 6). It has been recorded by Mr. Halbert from Ireland and 

 from the Norfolk Broads. 



4. Hydrachna schneideri, Koen. 



Female about 2 '6 mm. in length with oblong dorsal plate 

 much wider than long (Fig. 7). This species, which has not been 

 previously recorded as British, has been found on the Norfolk 

 Broads and in Epping Forest. The swimming hairs on the legs 

 are rather longer than those usually found on species of 

 Hydrachna. 



