San Martin (2005: 63) used a recombination of Sphaerosyllis bilineata into Prosphaerosyllis in text flow, not formally signified as a new usage, when discussing his recombination of Hartmann-Schröder's, 1979 Australian Sphaerosyllis species, as Prosphaerosyllis longipapillata. It is evident that if Prosphaerosyllis is recognised as a full genus (it was a subgenus of Sphaerosyllis), then that is where Sphaerosyllis bilineatea should be placed.
Faulwetter et al. (2011: 301) compared Prosphaerosyllis bilineata with Prosphaerosyllis longipapillata (Israel specimens, originally described from Australia) and infer they are very similar, a conclusion in line with discussions by previous authors. They state that: "To determine the identity of the Mediterranean material and whether P. bilineata and P. longipapillata are different species or not, careful examination of all type material is needed."
San Martín, G. (2005). Exogoninae (Polychaeta: Syllidae) from Australia with the description of a new genus and twenty-two new species. Records of the Australian Museum. 57(1): 39-152.
Faulwetter, S.; Chatzigeorgiou, G.; Galil, B.S.; Arvanitidis, C. (2011). An account of the taxonomy and distribution of Syllidae (Annelida, Polychaetes) in the eastern Mediterranean, with notes on the genus Prosphaerosyllis San Martín, 1984 in the Mediterranean. ZooKeys. 150(0): 281.