BRITISH HYDRACHNIDiE. 131 



1875. — Atax crassipes, Kramer, Beitr. zur Naturgesch. des 



Hydrachmder, p. 293, Twf. VIII., Fig. 4. 

 1879. — Atax crassipes, Lebert, Description D. Hydrachnides du 



Leman, p. 45, PI. XL, Figs. 10 — 10a. 

 1880. —Atax crassipes, C. J. Newman, Sveriges Hydrachnider, 



PI. XXL, Tab. I, Fig. i. 

 1882. — Atax crassipes, G. Haller, Die Hydrachniden des Schweiz., 



p. 76. 

 1885. — Atax crassipes, Krendowsky, Hydrachniden of Russia, p. 55. 



Average length of body, about i"2o mm. Average breadth, 

 about 0*92 mm. Average length of legs: — ist pair, 370 mm.; 

 2nd pair, 3-50 mm. ; 3rd pair, 2-56 mm. ; 4th pair, 3*30 mm. 

 Average length of palpus, 0*84 mm. 



Colour. — A pale yellow, with brown markings on the dorsal 

 side, with a yellow X-shaped piece in the centre. The eyes are 

 sometimes dark red and sometimes they are dark brown in colour. 



The legs in some cases are quite transparent and colourless ; 

 in others they are a deep slate blue. In the autumn of 1896 I 

 took some specimens in Wales, which were very deep in colour. 

 It was, no doubt, this difference in the colour which led Koch to 

 think they must be different species. The form of the upper 

 or dorsal side of body is a long oval, truncated on the posterior 

 margin ; at each angle of the truncated margin is a small projec- 

 tion (see PI. VII., Figs, i and 3). The projection on the legs I 

 consider a peculiarity of this mite. The legs are long ; the first 

 pair are thick at the first and second joints. These joints, or 

 rather internodes, are fitted with the powerful spines or hairs 

 which we find on no other mites but members of this genus. They 

 are thick near the body, and gradually taper towards the tarsi. 



The second pair of legs are the longest, which is a very 

 unusual thing in mites. The second pair measure 0*94 mm. 

 longer than the third pair of legs, and 0*20 mm. longer than the 

 fourth "pair. The second, third, and fourth pairs of legs are all 

 slender, and not at all like the first pair, in which the femur and 

 trochanter are so much enlarged. There are two claws to each 

 tarsi (see Fig. 6). 



Palpi (Fig. 4) are rather long, the second joint being the 

 thickest. The third is small. The fourth has three pegs — two on 



