She had joined the Legal Draftsman's Department in 1978 and retired as senior deputy legal draftsman in July 2006.
"She has been extensively involved in drafting major legislation in Sri Lanka, having received specialized training in legislative drafting," the Central Bank said in a statement.
"She has also worked in the Indian Parliament in New Delhi and in the Law Drafting Division of the Department of Justice in Hong Kong."
Ramanathan was enrolled as an Advocate in the Supreme Court of Ceylon in July 1973.
The monetary board is now made up of Governor Nivard Cabraal who is its chairman, P B Jayasundera representing the Treasury and Tilak de Zoysa representing the private sector.
There is still another vacancy to be filled.
She has read for her post-graduate studies in