Marrella
Marrella was the first fossil collected by Charles Doolittle Walcott from the Burgess Shale, in 1909. Walcott described Marrella informally as a "lace crab" and described it more formally as an odd trilobite. In 1971, Whittington did a thorough redescription of the animal. On the basis of its legs, gills and head appendages, he decided that it was not a trilobite, nor a chelicerate, nor a crustacean.