Microfossils have been discovered in thin sections cut from a sample of black, laminated, nodular chert collected from the Neohelikian Dismal Lakes Group of the Dismal Lakes area, District of Mackenzie. Two distinct morphological forms are differentiated: filaments and spheroids. The filaments are further subdivided, on the basis of morphology, into four basic varieties: (1) septate, unbranched, uniseriate filaments composed of chains of spheroidal to ellipsoidal cells showing marked constriction between cells, (2) septate, unbranched, uniseriate filaments characteristically lacking constrictions between cells, (3) nonseptate, unbranched filaments of large diameter (> 1.8 μm), (4) nonseptate, unbranched filaments of small diameter (< 1.3 μm). The spheroidal structures occur singly, in pairs and in clusters, and some of them contain blebs of carbonaceous matter which may represent remnants of organelles, reflecting eucaryotic affinities.

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