Finlay was born in Comilla, India (now Bangladesh), on 22 March 1901, to a family of Baptist missionaries.
[1] His main research interest was marine and non-marine malacofauna of New Zealand, both recent and fossil.
[2] After graduation, Finlay ran into financial hardship, living off of research grants, and occasional work as a contract consultant for oil exploration companies.
[2] Finlay was appointed to the Geological Survey of New Zealand in 1937,[1] where he worked a micropaleontologist studying Foraminifera.
[1] Many of Finlay's works were published in Transactions and Proceedings of the Royal Society of New Zealand abbreviated as Trans.