Desmatractum

Abstract: IN studies of peat deposits from south-western Australia, a number of small fossil algae have been found with a morphology similar to certain living polyhedral unicellular species of the family Oocystaceae of the Chlorococcales. The classification of this family is artificial1 and is based on the type of colony produced. Genera which have been placed in the family include Tetraedron, Desmatractum, Octogoniella and Scotiella 1–3. Two of these, Octogoniella and Desmatractum, have a peculiar form characterized by two envelopes, separated by a more or less wide space containing an aqueous mucilage. The inner envelope is delicate, while the outer is composed of two conical halves joined together in the median plane.