The superfamily Eunicea (herein considered to include six families, p. 2) comprises one of the most diversified yet most closely allied among the numerous families of the order Polychaeta. More than any other group, save perhaps the elytral-bearing chaetopods including the polynoids and their relatives, they are related to one another by characters of unique distinction. These, however, are largely internal, some of the most significant being in the proboscidial armature. Externally the Eunicea differ from one another so widely that their affinities might not be surmised, as, for example, among species of the genera Diopatra
The distinguished Scottish zoologist, W. C. McIntosh (1910, pp. 343-352), has given a summarized account of the extensive studies devoted to this superfamily. Some of the earliest accounts were made by several renowned French scientists, including Savigny (1809), who erected the family and several genera; Blainville (1825 and 1828), whose classification was more detailed but based on unnatural affinities (placing genera from widely related families in the same category); and Audouin and M. Edwards (1834), who divided the group into 2 great divisions, the abranchiate and the branchiate. This last-named plan was later followed by Johnston (1865), Quatrefages (1865), and others.