An Unusual Diatom from the Antarctic

Abstract

DURING the cruise of M.V. Magga Dan under charter to the Antarctic Division of the Australia Department of External Affairs during January-April, 1959, phytoplankton samples were collected by a modified Hardy Indicator, and later examined at the Commonwealth Scientific and Industrial Research Organization's Division of Fisheries and Oceanography, Cronulla. In the course of this examination, a peculiar diatom was observed on two occasions in the same sample. In each case, one valve of a cell had the characters of Coscinodiscus, the arrangement of the areolae resembling that of C. lineatus; but the valve was deeply concave. The other valve was characteristic of Asteromphalus roperianus. In one example two cells were in contact, one having the mixed character described, the other being a typical Coscinodiscus, with both valves identical. The other example was solitary, and smaller (65µ compared with 100µ), showing that it belonged to another generation.