on 1 november 1956, under states reorganisation act, 1956, a portion of the purnea district east of the river mahananda and the purulia sub-district of the manbhum district in the south (except char thana) were transferred from bihar to west bengal. thus, assembly constituencies in west bengal increased from 187 (238 seats) to 195 (252 seats) during 1957 assembly elections.