Runcina ferruginean.sp. (Cephalaspidea: Opisthobranchia: Gastropoda), a new runcinid from Great Britain

Abstract

Members of the small suborder Runcinacea have recently been reviewed and efforts have been made to group new findings (Burn, 1963; Baba, 1967; Miller & Rudman, 1968). The following structures served for the classification: gills alone (Baba, 1967), gills, radula, gizzard-plates and shell (Burn, 1963). According to this classification a more detailed subdivision became necessary. Two proposals brought forward by Burn (1963) and Baba (1967) are in discussion (see below). Two new generaRunnicaandPseudoilbia(Miller & Rudman, 1968) have not as yet been definitely placed in a family. As a consequence of this grouping some of the former members of the genusRuncinahave been moved to another genus, e.g.Runcina elioti(Baba, 1937) toRuncinida(Burn, 1963) by reason of four or five gills surrounding the anus in a semi-circle, andRuncina setoensis(Baba, 1954; Ghiselin, 1963) toMetaruncina setoensis(Baba, 1967) because of its single gill and a greatly reduced radula (compare Table 1).