Bibliographic source, museum catalog numbers and type locality are given for ready reference. Synonyms are enclosed in brackets. New synonyms are preceded by an asterisk, uncertain ones by a question mark. Comments are made only on those types where changes of name are made and which have not been treated since first described.
In some specimens, for example the Ehlers' 1868 types, it is not certain that the specimens designated "types" are actually the holotypes. Also, with several of the Chamberlin, 1920 types, para types are included because it is not certain that the holotypes are still extant. A considerable number of types that have been reported as deposited in the Museum have not been found in the collections. They are not included in this paper. Many of the Ehlers' 1887 types, from Florida and vicinity, are dried or badly disintegrated. Little can be added to what is known of them without further collecting in the type localities.
Two genera of the family SABELLIDAE which are represented by species in considerable confusion, and for which important type materials are in the Museum, are taken up separately at the end of this paper. These genera are Eudistylia
Bush and Pseudopotamilla
Thirty families of polychaetous annelids out of a total of fifty-seven families are represented by types in the Museum. These include 160 species, of which 40 are here regarded as synonyms. Eleven others are questionably synonyms also. This leaves a total of 119 types of valid species.