BeRMS source details
Pettibone, Marian H. 1956. Marine polychaete worms from Labrador. Proceedings of the United States National Museum, 105(3361): 531-584.
51333
Pettibone, M. H.
1956
Marine polychaete worms from Labrador
Proceedings of the United States National Museum
105(3361): 531-584
Publication
Kristian Fauchald's Polychaeta DB
Available for editors 
Ephesia gracilis Rathke, 1843 accepted as Sphaerodorum gracilis (Rathke, 1843) (source of synonymy)
Harmothoe impar (Johnston, 1839) (source of synonymy)
Harmothoe impar (Johnston, 1839) (source of synonymy)