Type species appears to be first selected by Pettibone (1957:160) as Anthostoma ramosum. Anthostoma hexaphyllum was described by Schmarda at the same time.
Pettibone, Marian H. (1957). North American genera of the family Orbiniidae (Annelida: Polychaeta), with descriptions of new species. Journal of the Washington Academy of Sciences. 47(5): 159-167. available online athttp://biodiversitylibrary.org/page/39753529 Available for editors [request]