[None. Introduction starts as:]
The polynoid genera
Polyeunoa McIntosh (1885) and
Hololepidella Willey (1905) have been used by various polychaete workers to include identical species. The species referred to the two genera are generally elongate, with numerous segments and numerous pairs of elytra. In addition, the lateral antennae are inserted ventrally on the prostomium, i. e., harmothoid type of insertion. The elytra in the posterior segments may be rather irregularly arranged in these elongate species. In a study of numerous specimens of the type-species of
Polyeunoa,
P. laevis McIntosh, Bergström (1916) pointed out the unusual variability in the number and arrangement of the elytra. At the same time, he suggested that
Polynoe tuta Grube and
Hololepidella commensalis Willey might both be referred to
Polyeunoa, since these two species also show variability in the arrangement of the elytra in the posterior regions. The elytral variability was well shown for
Polynoe tuta (as
Halosydna) by Johnson (1901). Augener (1918, 1922) suggested that
Hololepidella be used for polynoids with a harmothoid prostomium and numerous elytra extending along the body. Neither Bergström nor Augener emphasized differences in the arrangement of the elytra in the anterior region or other parapodial differences. Berkeley and Berkeley (1948) and Pettibone (1953), following Bergström, referred
Polynoe tuta Grube to
Polyeunoa McIntosh; emended Bergström. The same species was referred to
Hololepidella, following Augener, by Annenkova (1937), Hartman (1948), and Uschakov (1955). Similarly,
Polynoe nigropunctata Horst was referred to
Hololepidella by Day (1957) and to
Polyeunoa by Day (1967). Thus, it was more or less generally understood that the arrangement of the elytra in these elongate species was so variable that their exact arrangement was not especially important and, as such, often was not included in the original descriptions.