Synoptic Keys to the Genera of Ophiuroidea
When the last monographic treatment of the Ophiuroidea was published by Lyman in 1882, 103 genera were recorded. Since then a further 205 genera have been proposed (many of them evident synonyms), yet no comprehensive revision of the group has been attempted. As a result the whole literature of the subject has become extremely scattered and systematic studies are now very laborious. The synopsis of existing genera here presented is an attempt to give a preliminary analysis of the generic characters in a form suitable for use by those engaged on regional faunal studies. Of the 308 genera which have been recorded, some 53 genera are provisionally rejected as synonyms, leaving about 255 valid genera which embrace some 1,900 species. The characters have been keyed in a numerical system which should be followed consecutively. At every point the contrasted character is cited by its serial number in parentheses. It is hoped that in this way practical identification and cross-checking will be simplified, at the same time retaining a reasonably natural sequence. The key avoids the use of characters which require the destruction of the specimen for their demonstration. Wherever feasible, external characters are employed, so that unique specimens may be subjected to the minimum of damage in the process of identifying them. For this reason Matsumoto's classification has been largely abandoned, as it is impracticable. The arrangement here adopted is an arbitrary development of various proposals already current in the literature. The nominotypical rule has been applied throughout to the family-group taxa. Thus, in the case of the type genus Ophiura Lmk., Ophiuridae Lyman replaces Ophiolepididae as the familial name, Ophiurinae Lyman replaces Ophiomastinae as the subfamilial name; in accordance with the rule, both are attributed to 1865, the original date of publication by Lyman of the familial name, which in any case has priority. For other groups of ophiuroids the original names for the families and subfamilies have been restored if valid. Where a genus appeared to me to be unsatisfactorily defined, the type species has been used as the basis of the generic diagnosis. Thus, it has been felt preferable to indicate that the type species of a genus has "3 erect arm-spines", rather than "arm-spines present, few". Where possible, expressions such as "broad", "long", etc., have been replaced by more quantitative values—e.g., "as broad as a basal arm-joint", "longer than two arm-joints", etc. In many cases, unfortunately, these details cannot be ascertained from the literature. The original diagnosis and authority and the name of the type species is cited for each genus. The type-species is indicated by a prefixed asterisk; it gives the name as originally published, but the trivial name alone is cited in those page 2cases where the species is still placed in the genus to which it was originally referred. For each type species there is also given some indication of the origin or distribution, if known, and an approximate bathymetric datum. Thus, a type species from "Albatross Station 4781 in 482 fathoms" is cited as "N. Pacific, 500 fms". Utilizing the cross-reference provided by the key itself, the bibliography, and the index, the original source for each genus can be found. Where the source of a type species differs from that of the genus of which it is now the type, in the more important cases it will be found included in the bibliography; otherwise, reference should be made to H. L. Clark's "Catalogue of Recent Ophiurians" (1915), or the Zoological Record in the case of species published since 1915.
This guide to the genera is necessarily derived from the original work of others, and represents a digest of the very scattered literature. Most of the genera are known to me only through the literature. It seems inevitable that errors will have crept in during the long process of abstracting and rearranging, and I shall be grateful for corrections and for information on any genera which have been omitted, in order that a supplement may be prepared if it seems desirable. A new monograph is urgently required, but could only be undertaken by someone with access to the great collections held in museums of the northern hemisphere.