Complex sentence: William Theobald (1829-1908) was a British malacologist and naturalist, staff of the Geological Survey of India then based in Burma, which was still a part of British India.
Split into simpler sentences: William Theobald (1829-1908) was a British malacologist and naturalist on the staff of the Geological Survey of India. That organization was then based in Burma, which was at the time still a part of British India.