Difflugia bacillariarum Perty, 1849
Diagnosis: shell transparent, colorless or light yellow-brown, ovoid, spherical or pyriform usually with one or two prominent spines, usually pointed, of varying length, and positioned centrally, but it may be deflected to the side when the tapering is uneven; shell composed of thin siliceous plates overlaid by diatom frustules, which are united by an organic cement.
Dimensions: Length 57-103 µm (Ogden); 67-133 µm (Hoogenraad and De Groot, 1940).
Ecology: Sphagnum pools. Rare.
Remarks: It is thought that the basic shell is made of small shell plates and that the diatoms act as reinforcement. The organic cement is seen either as area of a patterned structure of small rings, or as strands between particles. The shape of the aperture is dependent on the arrangement and size of the diatoms which surround it. Small diatoms are usually used and the shape is circular, but it may vary to the extent of being triangular. Chardez (1978) observed that the aboral horn was either present or absent in specimens of D. australis (Playfair, 1918), a species that was initially described as a variety of D. bacillariarum. Although D. australis is alleged to differ from D. bacillariarum in size, the range of measurements given by Playfair (1918) for Australian species of both species are similar. Furthermore, Playfair noted that one specimen of D. bacillariarum australis was formed entirely of nebeloid plates, which supports the observation made above regarding the inner shell and diatom reinforcements.