In Haddonfield, New Jersey were marlpits, where a dinosaur skeleton was discovered in 1858 by William Foulke and named "Hadrosaurus foulkii" by Dr. Leidy of Philadelphia's Academy of Natural Sciences. Cope found more fossils in the marlpits there. For example, he described "Elasmosaurus platyurus" and "Laelaps" in 1868. Edward Cope also went on expeditions to caves; the last cave he visited was the Wyandotte Caves in Indiana in 1871.