44 Fresh- Water Mites. [Sess. 



The genus Eulais, once spelt Eylais, which contained at one 

 time only a single species — E. extendens — now includes about 

 fifty. The principal point of identification is the eye-plates. 

 All the feet have claws, but the fourth pair of legs are with- 

 out swimming hairs. Both male and female are alike in 

 structure. The one I send as a specimen is Eulais georgei, 

 Soar (Plate IV. fig. 3 : A, dorsal surface ; B, epimera and 

 mouth-organs ; C, mouth-organs on larger scale ; D, view of 

 inner side of palpus. The skin of these mites is very soft 

 and easily broken. They often swim for a long time ventral 

 surface upwards, trailing the fourth pair of legs, which are 

 not used for swimming, behind them. The eye-plates are not 

 shown on this drawing, but figures are in ' Science Gossip.' I 

 have not heard of it having yet been found in Scotland. 



Pionacercus vatrax, Koch (Plate IV. fig. 4, is the male). In 

 this species we have a spur on the fourth segment, as in 

 the Arrhenuri, with the addition of a peculiarly developed 

 foot. It is a very small mite, not common. P. leuckarti 

 (Piersig) has been found by Mr Williamson at Bavelaw Moss. 



Hygrobates longipalpis, Hermann. The members of this 

 genus are nearly always found in running water. They are 

 very common. Three species only are known in Great Britain 

 at present. Piersig gives eleven known species in * Das Tier- 

 reich.' The male and female are alike except in the genital 

 plates, which I have shown in the drawing (Plate V. fig. 1 : 

 A, male ; B, female). They are powerful swimmers, but are 

 without the swimming hairs at the joints of the legs which 

 we find in other swimming mites. I have had a great many 

 from Scotland. 



Hydryphantes frici, Thon (Plate V. fig. 2). This genus is 

 noted for a chitinous plate on the dorsal surface between the 

 eyes, and it is on the shape of this plate that in several cases 

 identification lies. In others it is the shape and number of 

 the discs on the genital area. I send this because the only 

 specimen I have seen was found in Scotland by Mr Taverner. 



Pseudosperchon verrucosa, Protz (Plate V. fig. 3). The 

 name of this genus has been altered by Piersig from Sperchon- 

 opsis. There is only one species known at present. The first 

 was found in Saxony by Protz in 1896. The only specimen I 

 have seen was found by Mr Taverner in Scotland. It has no 



