of Marsh that Cope had mistakenly placed the head of a fossil Elasmosaurus on the tail, rather than on the neck, and then publishing a correction. Leidy was an early American supporter of Darwin's theory of evolution, and lobbied successfully for Darwin's election to membership in the Academy of Natural Sciences of Philadelphia. In 1852, Leidy referred Bison antiquus, the North American fossil bison, to the genus Bison, the first to do so. Sometimes called the "ancient bison", it was the most common large herbivore of the North American continent for over 10,000 years, and is a direct ancestor of the living American bison. Leidy dominated vertebrate paleontology research in Florida during the latter half of the 19th century. He described and published the newly discovered species Smilodon floridanus. The "Soap Lady" In 1875, a woman's body was exhumed from a Philadelphia cemetery; her body was encased in adipocere, a fatty substance that forms in warm, alkaline environments without exposure to oxygen. Examining her, Leidy originally reported that she had died in the 1793 Philadelphia yellow fever epidemic, but X-rays taken in 1987 showed that she had buttons on her body that weren't produced until the 1830s. Similarly, the body didn't have teeth, so Leidy thought the woman had died in middle or old age; however, a new set of X-rays in 2007 suggested that the woman had died in her late 20s. Wagner Free Institute After William Wagner's death in 1885, the Wagner Free Institute of Science formed a board of trustees to find a new director. They chose Leidy to lead the institute, and he became president of the institute's faculty and curator of the museum. He held this position while remaining curator at the Academy of Natural Sciences and professor at Penn. Under Leidy's direction, the Wagner became a more professional institution for research and education. He formed the institute's professional journal "Transactions of the Wagner Free Institute of Science" and sponsored expeditions to collect specimens. One famed expedition to western Florida led by Angelo Heilprin led to the first discovery of a saber-toothed cat in North America. Leidy also led a large renovation to the building and dramatically reorganized the collection. The exhibition he designed opened in 1891, and displayed specimens based on taxonomy and systematics. Today, the Victorian cases and hand-labelled specimens remain almost unaltered since Leidy's reorganization in the late 19th century. Other scientific