47 



An Unrecorded Hydrachnid found in North AYales. 



By Chas. D. Soar, F.R.M.S. 



{Read January IHth, 1901.) 



Plate 5. 



The mite which I now bring before your notice was found in 

 the upper tarn, Cwm-Glas, Snowdon, on September 6th, 1896, 

 during an excursion for collecting purposes, by Mr. Scourfield and 

 myself. Two males and two females were taken. When first 

 found I took them to be Pionacerciis leuckarti described by Piersig 

 in 1894. But in September 1899 Dr. George, of Kirton-Lindsey, 

 •sent me a male and a female to examine which proved to be the 

 true Pionacerciis leuckarti ; I then found out that mine was quite 

 a different species. After spending some little time in making 

 sure it had not been previously described, I decided to bring it 

 before you as a new species of that genus. 



Pionacercits is a genus which occupies an intermediate j)osition 

 between Piona and Acercus. It differs^ from Piona in that the 

 males have the tarsi, or last segment of the fourth pair of legs, 

 much modified, whereas in Piona it is the fourth segment w^hich 

 is peculiar in structure. The other characteristics are the same. 

 It differs from the Acercus in having only three discs on each 

 genital plate, while in Acercus there are a large number. Its 

 other features show very little difference. 



The characteristics of the genus Pionacercus are : Body-skin 

 soft ; eyes wide apart ; claws to all feet ; swimming hairs on 

 legs ; three discs on each side of the genital fissure ; a small peg 



