[7] She completed her doctoral studies in 1928, and was awarded a PhD from the University of Cambridge in 1930, with a thesis on crabs collected by the English zoologist Cyril Crossland on the St. George expedition to the Pacific in 1924.
She published a number of scientific papers on these topics, including the description of three new species of mites that she found on spiders, snakes and sea lions.
[11][12][13][14] She gave regular public talks on spiders and scorpions on Sunday afternoons at the Natural History Museum.
[17] In 1932, Finnegan described three specimens of a new scorpion that had been collected by the British explorer Bertram Thomas from the Rub' al-Khali in the southern Arabian peninsula.
Campbell Smith worked in the department of mineralogy of the museum, and Finnegan was required to resign her post in order to marry, as a consequence of the Civil Service marriage bar that was then in place for women in the UK.