280 C. D. SOAR ON THE GENUS HYDRACHNA. 



easily known by the two small elongate plates on the body skin 

 near the inside edge of the eye-capsules (Fig. 11). 



15. Hydrachna maculifera, Pier. 



Mite red, with dark markings on dorsal surface. Female 

 about 2 "4 mm. in length. This mite has small plates just 

 behind the eyes. Recorded from England and Ireland (Fig. 18). 



16. Hydrachna comosa, Koen. 



Female about 3 mm. long. Third and fourth pairs of epimera 

 short and wide. The eye-plates in this species become long 

 bent ridges of chitin (Fig. 19). Norfolk Broads. This is the 

 first record of this species as British. 



17. Hydrachna bivirgulata, Pier. 



Female about 3*2 mm. This species is very rare, having only 

 been taken at present from the Norfolk Broads area (Fig. 24). 



18. Hydrachna halberti, n.s. 



A large mite, deep red in colour; female 5*2 mm. long. 

 Genital area with a deep inbaying. Skin covered with rounded 

 papillae. On reference to Fig. 21, and comparing it with 

 Fig. 22 (//. incisa, Halbert), it will be seen that the chitinous 

 plates, or muscle attachments, behind the eyes are very much 

 alike in both species, except that in H. halberti the plates are 

 close behind the eyes, whereas in H. incisa they occupy a central 

 position. This species was found in Osborne Dyke, Norfolk 

 Broads, by Mr. Browne. 



19. Hydrachna williamsoni, n.s. 



Male about 3*9 mm., dark red, with darker markings on 

 dorsal surface. There are no plates or muscle attachments 

 between the eyes and hair glands such as will be seen on Figs. 21, 

 22, 23, but a clear space (Fig. 20). The genital plates have 

 two acetabula, one on each side, much larger than the others. 



