DIFFLUGIA BACJLLARIARUM. 25 



9. Difflugia bacillariarum Perty. 

 (Figs. 45-47.) 



Difflngia ' bacillariarum PERTY in Mittli. nat. Ges. Bera, 



1849, p. 27; and Kenntn. kleinst. Lebensf. (1852), 



p. 187, t. ix, f. 7 ; CLAPAREDE & LACHMANN Etudes Inf. 



et Rhi/. I, 2 (1859), p. 448. 

 Difflugia elegans PENARD (pars) in Mem. Soc. Geneve, XXXI 



(1890), 2, p. 140, t. iv, ff. 4, 5, 11; Faune Rhiz. Leman 



(1902), p. 236, ff. 12, 13 (p. 237). 

 Difflugia acuminata var. elegans G. S. WEST in Jrn. Linn. 



Soc., Zool. XXVIII (1901), p. 319, t. xxviii, ff. 11, 12. 

 Diffliujia Solowetzkii G. S. WEST in Jrn. Linn. Soc., Zool. 



XXIX (1903), p. 113; AVERINTZEV (pars) in Trudui 



S.-Peterb. Obshch. XXXVI (1906), 2, p. 189. (Non D. 



Solowetzkii MERESCHKOWSKY in Arch. mikr. Anat. XVI 



(1878), p. 194, t. x, f. 17.) 



Test chitinous, transparent, covered, as a rule, with 

 minute diatom-frustules and some sand-grains, scattered 

 or aggregated ; broad in proportion to its length, and 

 symmetrical, at the mouth about two-thirds the width 

 at its broadest part ; the convex sides sloping evenly 

 downwards from the crown, without constriction or 

 dilation ; the acute or conical crown terminated by a 

 protuberance which is erect or deflected at an angle, 

 hollow and frequently perforated at the apex. Nucleus 

 and pseudopodia normal ; the latter usually simple. 



Dimensions: 94-100 /x (West). 



Wicken Fen, Cambs; Llyn-y-cwm-ffynon, N. Wales; 

 and Rhiconich, Sutherlandshire (G. S. West). 



Difflugia bacillariarum (first described by Perty under 

 this name in 1849) is a variable species, making with 

 its variety elegans {Difflugia elegans Penard) a group of 

 forms as difficult to determine as are the multitudinous 

 forms of D. constricta. Those which are comprehended 

 under the variety elegans have one feature which 

 is rarely absent the test has a slight constriction 

 above the mouth, causing that to appear dilated. 



We have included in typical bacillariarum the form 



