Jean Baptiste d'Omalius d'Halloy (1783 - 1875) was a Belgian geologist and wealthy Catholic aristocrat who became one of the best known advocates of evolutionism in Belgium and France in the mid-nineteenth century. His conservative credentials and rejection of strict materialism would enhance the reception of evolutionary thought.
As a young man, d'Omalius moved to Paris and studied under Lamarck and other French evolutionists including LaCepede and Etienne Geoffroy St. Hilaire). Beginning in 1831, d'Omalius argued in his Elements de Geologie that the fossil record could best be explained by a theory of evolution (as opposed to a series of mass extinctions and subsequent independent creations). In the 1840s and 1850s, d'Omalius published a number of papers on the succession and modification of living beings (e.g., 1846, Note On the Succession of Living Beings). Ultimately, d'Omalius, while not rejecting Darwin and Wallace's principle of natural selection, viewed it as being unable to account for large morphological changes over the course of geological time.
For an excellent treatment of d'Omalius d'Halloy, his ideas on evolution, and the broader societal context of his evolutionism please read: de Bont, R. 2007. A serpent without teeth. The conservative transformism of Jean-Baptiste d'Omalius d'Halloy (1783-1875). Centaurus 49: 114 - 137. pdf here