390 British Hydrachnidcs : The Gemis Fiona. [Sess. 



KEY TO HELP IDENTIFICATION OF SPECIES OF PIONA. 

 FEMALE. 



1. With acetabula entirely free, none on special plates. 



21. Fiona aduncopalpis $ 

 With acetabula partly free and partly on special plates . . 2 

 With acetabula entirely on special plates 4 



2. With one sickle-shaped genital plate on each side of genital 



fissure, and one or more acetabula free within the curve of 



the plate 3 



With two plates on each side of genital fissure, sickle-shaped, 

 with division, and one or more free acetabula. 



19. Fiona paucipora ? 

 Nearly all acetabula free, 3 or 4 only on small hair plates. 



17. Fiona conglobata ? 



3. All chitinous parts a brownish yellow and 15 to 20 acetabula on 



each plate 7. Fiona rotunda $ 



Chitinous parts generally blue, with 18 to 25 acetabula on each 



plate .4. Fiona obturbans ? 



With from 30 to 40 acetabula on each plate 6. Fiona rotundoides ? 



With from 50 to 60 acetabula on each plate . 5. Fiona disparilis $ 



4. With two plates on each side of genital fissure .... 5 

 With one sickle-shaped plate on each side of genital fissure . 6 

 With one disc-shaped plate on each side of genital fissure . . 7 

 With one tongue-shaped plate on each side of genital fissure . 8 

 With one large irregular-shaped slate-blue plate on each side of 



genital fissure, ha\'ing a large number of small acetabula, two 

 being distinctly larger than the others 11. Fiona longipalpis ? 



5. The two posterior plates irregularly tongue-shaped, having 



about 20 acetabula each ... 10. Fiona discrepans ? 



The two posterior plates irregularly tongue-shaped, having 

 about 10 acetabula each 15. Fiona rufa $ 



The two posterior plates sickle-shaped, having about 13 aceta- 

 bula each 16. Fiona circularis ? 



6. Irregular sickle-shaped plates, having about 9 acetabula each. 



1. Fiona fuscata ? 

 With much wider irregular sickle-shaped plates, having about 

 17 acetabula each 2. Fiona laminata $ 



7. Genital plates disc-shaped, with two acetabula larger than the 



others on each plate. Palpus with four or more hair pegs 



on flexor edge of fourth segment . . 20. Fiona uncata ? 



