Sars (1910: 339) proposed Psammis for its type (by monotypy) and only species P. longisetosa Sars, 1910 collected from Farsund in southern Norway. The genus has seen the addition of four species since, i.e. P. borealis Klie, 1939 collected north of Iceland, P. kliei Smirnov, 1946 from the East Siberian Sea, P. longifurca Bodin, 1968 from the Bay of Biscay and P. longipes Becker, 1974 from the Peru – Chile (Atacama) Trench (Klie 1939, 1941; Smirnov 1946; Bodin 1968; Becker 1974). Wells (1967) had previously expressed doubts about the validity of the genus, arguing that the only character that separates it from Danielssenia is the number of setae on the exopod of P5; however, Gee (1988) pointed out that species of both genera are probably trophically isolated as indicated by differences in mandibular gnathobase morphology and that this—in conjunction with the fused rami of P5—constitutes sufficient evidence for maintaining the genera separate. Huys & Gee (1993) redefined the boundaries of Psammis and restricted it to its type species and P. longipes. While P. longifurca was fixed as the type of the new genus Bathypsammis Huys & Gee, 1993, both P. borealis and P. kliei were tentatively maintained as species incertae sedis in the Paranannopidae (= Danielsseniinae; cf. Huys 2009) pending further re-examination. In subsequent contributions Gee & Huys (1994) assigned P. kliei to the genus Mucrosenia Gee & Huys, 1994 as species incertae sedis and Huys and Gee (1996) designated P. borealis as the type (by original designation) of their new genus Anapophysia Huys & Gee, 1996. The original descriptions of both sexes of P. longisetosa by Sars (1910: 339–340, plate CCXXV; 1921: 94–95, plate LXV.) were supplemented and largely superseded by a number of subsequent re-examinations including those by Gee (1988: 181–187, Figs. 1–4), Huys and Gee (1993: 72, 75, Figs. 21–22) and Huys et al. (1996: 248–249, Figs. 93B, 98, Table 4).