Class Maxillopoda, the barnacles, are stationary marine crustaceans with a hard exoskeleton covering most if not all of the animal. They attach to hard substrates, sometimes other living animals such as whales, and filter feed with long, feathery appendages called cirri.
Newman, W. A. et al., 1969. Cirripedia in Moore, R. C., ed., Treatise on Invertebrate Paleontology, Part R, Arthropoda 4(1), Volume 1. The University of Kansas and Geological Society of America. 398 pp.