a1 Department of Geology, University of Calcutta, 35, Ballygunge Circular Road, Calcutta 700019, India
Biplanispira Umbgrove is closely related to Pellatispira Boussac, from which it probably arose by the subdivision of the median chambers by the rapidly expanding marginal crest and the development of planispirally arranged secondary chambers on both sides of the peripheral flange. The genus appears to be polyphyletic, its species having been derived from different representatives of Pellatispira. Illustrated records of Biplanispira are confined to the region between eastern India and Eua, Tonga, and the genus appears to be restricted to the middle and upper parts of the Upper Eocene. In the Upper Eocene of the Garo Hills, eastern India, it is represented by B. hoffmeisteri (Whipple) and in the Andaman Islands by B. mirabilis (Umbgrove). This is the first record of the genus from mainland India.
(Received August 15 1983)
(Accepted November 14 1983)