QUADHULA lEEEGULAElS. 133 



Quadrula acolis Jawoeowsky in Arch. Naturgesch. I (1905)^ 



61, p. 320, t. XV, fe. 15-20. 

 Quadrula irregularis var. globosa Zschokke in Arch. Hydro- 



biol. II, 1 (1906), p. 6. 



Very minute ; in broad view compressed, and usually 

 discoid, without any perceptible neck, and, as in the 

 preceding species, composed of transparent chitinous 

 membrane Avith a surfacing of square plates, obliquely 

 arranged, inostly uniform in size and set in close order. 

 In lateral vie w narrowly ovoid (but varying in the degree 

 of compression), slightly notched at the mouth ; dorsal 

 and ventral views elliptic, the mouth either narrowly 

 elliptic or presenting the appearance of a slit with 

 parallel sides. Plasma colourless or faintly granular ; 

 a few minute yellowish-green corpuscles usually present, 

 and a distinct contractile vacuole ; the nucleus scarcely 

 visible ; the pseudojjodia few, thin, flexible, transparent, 

 and simple. 



Dimensions : Longest diameter 30-38 /x. 



Amongst Sphagnum in marshy ground ; and in tufts 

 of moss on wet rocks; much less common than the 

 preceding. On a dripping canal wall at Keatley, 

 Cheshire, 1891 ; Knutsford Moor, Cheshire. Peny- 

 ghent, "West Yorkshire [G. 8. West). Perwick Bay, 

 Isle of Man, 1891. Loch Ness, Scotland (D. J. 

 ScourfieU). Ireland, 1877 {W. Archer). Killpugh, 

 Co. Wicklow, Ireland, 1908 (/. Hophnson). 



In the Isle of Man this organism occurred in abun- 

 dance, in the locality mentioned, associated with various 

 other rhizopods not usually found in such situations. 

 A drop of water squeezed from a tuft of moss found 

 growing in the crevices of rocks facing the sea, often 

 contained a dozen or more individuals, besides empty 

 tests. The latter exhibited the structure very clearly. 



From Q. sijmmetrica the species differs both in size 

 and form. The quadrangular plates are proportionately 

 smaller on the smaller test, but they agree in the oblique 

 arrangement. Only in var. globiilosa Pehard — a variety 



