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Difflugia acutissima

 

Five shells from the same sample; the fourth shell is in lateral view, with biconcave sides; the fifth shell has two spines; 225-265 µm.

 

Difflugia acutissima Deflandre, 1931

Diagnosis: shell elongated ovoid with a short more or less distinct neck; fundus tapering into a sharp spine; shell composed of quartz particles, sometimes mixed with fragments of diatom shells; pseudostome circular.

Dimensions: Deflandre: length 178-233 µm; my measurements 210-265 µm (n>15).

Ecology: I have found this species in sediments of a ditch in the nature reserve Naardermeer, the Netherlands. Some shells were compressed, with a biconcave shape, as characteristic for Difflugia biconcava, present in the same location.

Remarks: Deflandre in his description compared the shape with a truncated cigar. This species can be distinguished from Difflugia acuminata by its short distinct neck and the sharp tapering spine.

Gauthier-Lièvre and Thomas (1958) described a variety gigas that they collected in Algerien and Tchad, Africa, with following dimensions: height 260-295 µm, diameter 100-190 µm. My measurements fit between the type and the variety.

Difflugia acutissima
Difflugia acutissima, after Deflandre, 1931
Difflugia acutissima gigas
D. acutissima var. gigas, drawing by Gauthier-Lièvre et Thomas, 1958

  

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