Crinoids, commonly known as sea lilies and feather stars, are abundant and diverse in many marine environments. Yet, because they are difficult to maintain in aquaria, have never been bred in the laboratory, and because many species are known from few specimens, they remain among the least understood of marine animals. Recognition of crinoid species is particularly ambiguous. Yet, accurate identification of these animals is critical for: 1) understanding their roles in marine ecosystems, where some may be harbingers of environmental change; 2) collecting specimens as potential sources of new pharmaceutical products, and 3) understanding their extensive fossil record. To clarify what constitutes a crinoid species, we will compare how genetic compositions (i.e., DNA) vary relative to the physical, or morphological, traits currently used to differentiate species in traditional taxonomic classification. Much of the crinoid body is plankton-feeding apparatus, which varies with growth and environmental conditions (e.g., current velocity). Analysis of specific portions of crinoid DNA will clarify the identities of 1) similar forms that differ in different habitats or at different depths, 2) unusually variable species, and 3) multiple species that may be growth stages of one species. DNA sequences should be similar within a species and differ between species. Analytical methods will follow established protocols already used successfully by us to study crinoids and other organisms. We will disseminate results via at least two peer-reviewed scientific journal articles and one international conference presentation. The interdisciplinary component of this project is a lecture series and hands-on laboratory for the University School science program that covers 1) taxonomy, evolution and the species concept, 2) crinoid ecology, 3) crinoids in the early history of deep-sea exploration, and laboratory exercises in taxonomy, identification and analyses of deep-sea skeletal remains using crinoids as a model.