Marrella

Marrella splendens is an arthropod known from the middle Cambrian Burgess Shale of British Columbia. It is the most common animal in the Burgess Shale.
History.
"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.
"Marrella"-like organisms are found in other Cambrian deposits. They are known from sediments as late as the Devonian.