48 C. D. SOAR ON AN UNRECORDED HYDRACHXID 



on the inner edge of the palpi near fifth segment ; and the last 

 segment of the fourth pair of legs much modified. 



Piersig in his great work on water-mites (Deutschlands 

 Hydrachniden) describes two species from Germany, Pionacercus 

 leucharti (Piersig), and P. uncinatus (Koenike). Both of these have 

 been found in Great Britain and recorded in " Science Gossip '^ 

 for 1900. Also one other described by Koch, Pionacercus vatrax^ 

 It is not in many genera that we can boast of more species than 

 they can in Germany, but with the species here described we now 

 have four as against two only known in Germany. 



Description of Male. Body. — Length about 0*52 mm. 

 Breadth about 0*40 mm., of a bright orange colour with brown 

 marking on the dorsal surface. The general outline of the body 

 is pear-shaped. This shape is not common with the Hydraclmids, 

 Acercus liliaceios (Miiller), is the nearest in form to this one, but it 

 is not so pointed at the posterior extremity. The skin of the 

 body is soft, but not so soft as we find it in Diplodontus and Eylais^ 

 It also appears much tougher at the apex than in the anterior 

 portion. The eyes are wide apart and very distinct, being almost 

 black, so that they show well on the orange-colour of the skin. 

 There are two rows of glands on the dorsal surface. I have not 

 found any hairs near these glands, but it is quite probable there 

 are some, for they are nearly always found in that position on 

 other mites. 



Legs. — We find the usual eight legs with six segments to each. 

 Length of first pair about 0*56 mm., these have very few bristles. 

 The second pair show a few swimming hairs as well as bristles. 

 The third pair, which are the shortest, being only about 0*53 mm. 

 in length, are formed very much like the same pair in the male 

 of Curvi2)es. This pair has a large number of swimming hairs on 

 the fifth joint, the hook, or claws, on the tarsi being very small. 

 The tarsi have very few hairs, but in Pionacercus leucharti t\ns, 

 segment has a great number. The fourth pair of legs are 

 about 0"62 mm. in length ; they are very strong and have a large 

 number of hairs on tlie fourth and fifth segments. The sixth 

 segment is of a very peculiar structure, being crozier-shaped, 

 somewhat similar to the same segment in Acercus. It has nine 



