A review of the genera of the Rissoidae (Mollusca: Mesogastropoda: Rissoacea)
The family Rissoidae is defined, and a detailed diagnosis of the family is given. The characters of the shell (and protoconch), radula, operculum, head-foot and anatomy are described and discussed for the family and for each genus (where they are known). The Rissoidae is contrasted with other Rissoacea, and the relevance of genital characters in higher classification is discussed. The genera are reviewed in the light of new information on the anatomical, radular, opercular and head-foot characters as well as shell microsculpture and other aspects of shell morphology. Thirty one genera and 24 subgenera are recognized in the family. Four of the subgenera are described as new, and one new genus and species are also described. A further 106 genus-group taxa are listed as synonyms. Eleven family-group taxa are included in the synonymy of the Rissoidae, and two subfamilies (Rissoinae and Rissoininae) are recognized. Of the remaining 119 genus-group taxa referred to the Rissoidae by previous reviewers, four Jurassic genera are tentatively included in the family and the remaining 115 are included in other families. A phenetic classification of the genera is developed using a summary of unweighted characters. The Falsicingulidae is diagnosed and it is suggested that it is closely allied to the Pomatiopsidae. A new family is created for Epigrus Hedley.