Two new species of the Family Clausiidae, Likroclausia namhaensis n. gen. and n. sp. and Rhodinicola laticauda n. sp., were described from washings of polychaetes collected from an intertidal mud flat on Namhae Island in the Korea Strait and from an intertidal sandstone in Kyokpo in the Yellow Sea, respectively. The host of the former species is Dasybranchus caudatus Grube, but that of the latter is unidentified. Cladistic analysis of the family indicated that the 20 clausiid species should be kept in six groups, with Pontoclausia-group containing five species (antiqua, lobata, prima, tomis, wilsoni); Likroclausia-group, one species (namhaensis); Rhodinicola-group, three species (gibbosa, elongata, laticauda); Mesnilia-group, two species (cluthae, martinensis); Clausia-group, seven species (bacescui, curticaudatum, lubbocki, mirabilis, rugosum, thomassini, uniseta); and Pseudoclausia-group, two species (giesbrechti, longiseta). Each group is a monophyletic entity identified with one or more synapomorphies. Whilst the taxonomical status of the genera Indoclausia, Megaclausia, Pherma, and Seridium are unclear, it is unequivocal that the following four genera should be treated as valid taxa in the Clausiidae in addition to Clausia: Mesnilia, Pontoclausia, Pseudoclausia, and Rhodinicola. Also, both Doviella prima Rocha, 1986, and Clausia wilsoni Gooding, 1963, are transferred to Pontoclausia. Rhodinicola thomassini Laubier, 1970, should be transferred to Clausia for the time being.