Massachusetts-born Zoologist remembered for his theory of zoogenesis, which he outlined in a 1930 scientific work entitled The New Evolution: Zoogenesis.
After graduating from Harvard University, he began a decades-long career with the Smithsonian Institution's National Museum of Natural History.
He was responsible for identifying and scientifically classifying such species as the Mulga Parrot and the Lesser Antillean Macaw.
His first marriage, to Mary Wendell Upham, produced five children. After Upham's death, Clark married Leila Gay Forbes.
He and English scientist Raymond St. Leger both conducted research in the field of entomology.