W. George Ridewood was a lecturer in biology at St Mary's Medical School, University of London, in 1908, when he described "A new species of Cephalodiscus, (C. Gilchristi) from the Cape seas" in Marine investigations in South Africa (Vol. 4, pp. 173-192). The species was named after the South African marine biologist J.D.F. Gilchrist* and belonged to the class Pterobranchia, a small group of minute marine organisms living in colonies.
The author was presumably William George Ridewood, who was associated with the Department of Zoology at the British Museum (Natural History) at the time. He compiled a Guide to the gallery of fishes... (1908) for the museum, as well as Memorials of Charles Darwin; a collection of manuscripts, portraits, medals, books and natural history specimens to commemorate the centenary of his birth... (1909). Later he described the Pterobranchia collected by the Australian Antarctic Expedition of 1911-1914 in the expedition's Scientific reports (Sydney, 1918).
He is probably also the same person as Walter [error for William?] George Ridewood, who published 18 zoological papers before 1900, most dealing with the anatomy (especially the skeletal anatomy) of fishes, frogs and toads, in journals such as Anatomischer Anzeiger, Journal of the Linnaen Society, and Proceedings of the Zoological Society.