 Continuing to flow west north-westward through Poulton Pool until the river eventually discharges into Stokes Bay, King Sound which is north-east of Derby.The river was named in 1881 by a pioneer of the area, George Julius Brockman during an expedition in the Kimberley area looking for grazing land north of the Fitzroy River.He named the river after the granddaughter of John Septimus Roe, Mary Matilda (May) Thomson.