Studies on the free-living protozoan fauna of estuaries in the coastal zone of Tamil Nadu, India Author Bindu, L. text Records of the Zoological Survey of India 2021 121 1 61 75 journal article 10.26515/rzsi/v121/i1/2021/141506 2581-8686 13186453 20. Centropyxis orbicularis Deflandre, 1929 Material examined : Mi-154, 6ex. , Marakkanam estuary, 20.vii.2014 . Diagnosis : Shell brown and ovoid. Lateral view spherical, tapers towards the apical region. Shell surface usually rough, area around the aperture smooth; aperture invaginated, uneven in outline, two lateral internal extensions; test diameter 105-130µm. Distribution in India : Andhra Pradesh , Himachal Pradesh , Tamil Nadu , Uttarakhand .