Prionospio fallax Söderström, 1920: 235 –237 figs. 135, 144–145; Sigvaldadóttir & Mackie 1993: 207 –211, figs. 3–4 Prionospio (Prionospio) fallax: Johnson 1984:6.49–6.51, figs. 6–39, 6 – 40.
Material examined. ESFM –POL/05– 279, 7 specimens, 9 September 2005, Iskenderun Bay, G 1, 36 º 35 ΄ 37 ΄΄N, 36 º 11 ΄ 9 ΄΄E, 5 m, mud; ESFM –POL/05– 506, 20 specimens, 17 September 2005, Mersin Bay, G 7, 36 º 46 ΄ 46 ΄΄N, 34 º 39 ΄ 39 ΄΄E, 10 m, mud; ESFM –POL/05– 992, 7 specimens, 23 September 2005, Anamur, D 27, 36 º04΄ 28 ΄΄N, 32 º 53 ΄0 3 ΄΄E, 10 m, muddy sand; ESFM –POL/05– 861, 20 specimens, 23 September 2005, Mersin Bay, D 28, 36 º03΄ 37 ΄΄N, 32 º 53 ΄ 11 ΄΄E, 25 m, sand; ESFM –POL/05– 1438, 2 specimens, 26 September 2005, Antalya Bay, K 34, 36 º 50 ΄ 25 ΄΄N, 30 º 48 ΄ 30 ΄΄E, 5 m, sand; ESFM –POL/05– 1648, 1 specimen, 27 September 2005, Antalya Bay, D 39, 36 º 48 ΄ 49 ΄΄N, 30 º 37 ΄ 57 ΄΄E, 100 m, mud; ESFM –POL/05– 1749, 6 specimens, 30 September 2005, Finike, G 15, 36 º 17 ΄ 34 ΄΄N, 30 º09΄ 33 ΄΄E, 10 m, muddy sand; ESFM –POL/05– 1860, 1 specimen, 30 September 2005, Finike, G 18, 36 º 16 ΄ 31 ΄΄N, 30 º 10 ΄ 50 ΄΄E, 75 m, mud; ESFM –POL/05– 1989, 5 specimens, 30 September 2005, Finike, G 16, 36 º 17 ΄0 7 ΄΄N, 30 º 10 ΄0 2 ΄΄E, 25 m, sandy mud; ESFM –POL/05– 3195, 1 specimen, 3 October 2005, Kekova, K 44, 36 º 11 ΄ 26 ΄΄N, 29 º 50 ΄ 51 ΄΄E, 3 m, Zostera marina; ESFM –POL/05– 1516, 45 specimens, 5 October 2005, Fethiye Bay, K 50, 36 º 38 ΄ 40 ΄΄N, 29 º05΄ 30 ΄΄E, 5 m, muddy sand; ESFM –POL/05– 3196, 135 specimens, 6 October 2005, Fethiye Bay, G 27 36 º 37 ΄ 46 ΄΄N, 29 º06΄ 32 ΄΄E, 5 m, muddy sand; ESFM –POL/05– 1547, 1 specimen, 6 October 2005, Fethiye Bay, G 28, 36 º 37 ΄ 48 ΄΄N, 29 º06΄ 30 ΄΄E, 10 m, mud; ESFM –POL/05– 2361, 21 specimens, 7 October 2005, Göcek, K 53, 36 º 44 ΄ 20 ΄΄N, 28 º 55 ΄ 43 ΄΄ 3 m, Zostera marina.
Diagnosis. Specimen complate, 0.6 mm wide, 14.2 mm long, with 67 chaetigers. Color in alcohol opaque white. Prostomium anteriorly truncated, lateral margins slightly concave, posterior part forming a short caruncle extending to anterior margin of chaetiger 2. Two pairs of eyes; anterior pair small, spherical; posterior pair large, reniform. Four pairs of branchiae on chaetigers 2–5; first and fourth pairs pinnate, nearly equal in size; second and third pairs apinnate, shorter than pinnate pairs. Noto- and neuropodial postchaetal lamellae smallest on chaetiger 1; notopodial lamellae foliaceus, largest on chaetigers 3–4; rounded on following chaetigers. Neuropodial postchaetal lamellae largest in branchial region; subrectangular and ventrally pointed on chaetiger 2; squarish to rounded on anterior and middle chaetigers, becoming rather inconspicuous on posterior chaetigers. Dorsal crest present on dorsum of chaetiger 7 only. Interpapodial pouches absent. Ventral sabre chaeta first present on chaetiger 10, numbering 1–2 per fascicle. Multidentate hooded hooks first appearing on neuropodia of chaetiger 11, on notopodia of chaetigers 22–24.
Remarks. The Mediterranean specimens agree with the original and subsequent descriptions of the species (Söderström 1920, Sigvaldadóttir & Mackie 1993).
Ecology. The highest population density (1350 individuals.m - 2) of this species was found on muddy sand substratum at 5 m depth at station G 27 (Fethiye Bay).
Distribution. Northeast Atlantic, from northern Atlantic to Mediterranean (Sigvaldadóttir & Mackie 1993); western Atlantic (Johnson 1984); Mediterranean Sea (Ergen 1979; Çinar & Ergen 1999); 2– 440 m.