Rhamphobrachium Ehlers, 1887: 70.— Paxton 1986 a: 44. Paranorthia Moore, 1903: 448.
Type-species. Rhamphobrachium agassizii Ehlers, 1887: 70, by subsequent designation of Hartman, 1944: 47. Gender: neuter.
Diagnosis. The definition given by Paxton (1986 a) is here emended as follows: peristomial cirri present or absent; anterior two or three pairs of parapodia modified, moderately prolonged, hooks with two rows of moveable spines, chaetal sacs extending to chaetiger 20–60; branchiae present or absent.
Remarks. The genus was previously defined as having peristomial cirri, branchiae, and three anterior pairs of modified parapodia with chaetal sacs extending to chaetiger 30–60. The erection of a new subgenus for the three progenetic new species described below necessitated the present emendation. With the description of the new subgenus, Rhamphobrachium includes three subgenera which can be distinguished as outlined in the key at the end of the paper.