1906-1907-] British Hydrachnidcs : The Genus Fiona. 387 



21. Fiona aduncopalpis, Pier. 



Female. — Body about 1'30 mm. in length, of a light red 

 colour with dark -brown markings. Malpighian vessel a 

 light yellow colour, but sometimes very irregular in its 

 position on the dorsal surface. Legs a straw-yellow colour, 

 long and well supplied with swimming - hairs ; retractile 

 claws small. Palpus quite different from any previously 

 referred to in this communication (fig. 107). Second segment 

 very thick and strong, the extensor margin being carried 

 forward beyond the front of the flexor edge. Third segment 

 very short and small, making it almost impossible to open 

 the palpi more than is shown in figure. It is from this 

 hooked shape that Piersig named it. Two long hairs on 

 the flexor edge of fourth segment, one behind the other. 

 No genital plates, the acetabula being free on the ventral 

 surface in both sexes. This is a peculiarity met with in 

 no other British species of Piona ; P. conglobata, Koch., 5 , 

 comes very near to it in this respect, but it always has 

 one or more acetabula on hair plates. About 12 acetabula on 

 each side of genital aperture. 



3fale. — About 0'75 mm. in length ; a little darker in colour 

 than the female. Malpighian vessel more regular in shape 

 and position than in the female. Each of the third pair of 

 legs is terminated by a strong claw. Three swimming-hairs 

 on the distal end of patella of each of the fourth pair of 

 legs. (Plate XLV., figs. 105-111.) 



Localities. — Not common, but has been found in Lincoln- 

 shire and on the Norfolk Broads. 



22. Piona elegans, n. sp. 



This, to the best of my knowledge, is an undescribed 

 species. I cannot find any description which agrees with 

 it, neither will it fit in with Dr Piersig's key to this 

 genus. 



Female. — About 1*60 mm. in length. Colour a yellowish 

 brown; all chitinous parts a pale slatey-blue; very dark- 

 brown, well-defined and regular markings on dorsal surface. 



