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Description of Acanthocorbis asymmetricaCell solitary, planktonic. Protoplast 4 x 3 microns; flagellum 6-9 microns long, surrounded by a ring of tentacles. Protoplast lodged in a lorica 15 -20 microns long; diameter at level of anterior transverse costa approximately 8 microns. Lorica composed of 15-17 longitudinal costae, which converge at the posterior end to form a stalk (4-11 microns long). The location of the stalk deviates markedly from the long axis of the cell, giving it an asymmetrical appearance (hence the specific epithet). Each longitudinal costa consists of four costal strips. The longitudinal costae project anteriorly as free spines (one and a half costal strips long). Two transverse costae (separated by one-third of a longitudinal costal strip) encircle the lorica at the anterior end; the lowermost is connected to the junctions between the second and third longitudinal costal strips (counted from the anterior lorica end). A single transverse ring is attached to the junctions between the third and fourth longitudinal costal strips (counted from the anterior lorica end). The complexity of the strip arrangement in the posterior part of the lorica is somewhat variable, depending on the number of strips entering the upper part of the stalk.