Some new and little known phytoplankton forms from the West Indian Ocean

New records of Pterosperma spp., Pachysphaera spp. and Meringosphaera spp. are made from light microscope studies of cleared millipore filter disc samples from the West Indian Ocean. One new species and one new form of the genus Pterosperma are described from these samples. An occurrence of the newly described species, Pterosperma parvareopunctatum, is also recorded from the gut contents of an ostracod from a deep haul in the East Atlantic Ocean.