Odostomia turgida G.O. Sars, 1878

Figures 56-57

Odostomia turgida, n. - G.O. Sars 1878:202

Odostomia turgida G.O. Sars - Norman 1902; Høisaeter 1986

Odostomia cf. turgida G.O. Sars - Høisaeter 2009

Ptychostomon turgidum (G.O. Sars) - Kobelt 1903

Odostomia unidentata (Montagu) - van Aartsen 1987

Odostomia unidentata var. turgida G.O. Sars - Smith & Heppell 1991

Type material: NHMO D1082

Type locality: Lofoten, northern Norway, ca. 120-130 m.

Material seen: Norway - Nordland, 6 shs (+ photograph of holotype).

Diagnosis: Shell: Most easily recognized on the rapid expansion of the diameter of the first few teleoconch whorls. The helicoid protoconch is large and protruding and completely exposed (Figure 57). Soft parts: Not known. Operculum: Not known.

Biology: Not known.

Distribution: A few shells from Lofoten (around 68°N) (G.O. Sars 1878). In my material six shells from between 66° and 67°N. Not known outside Norway.

Remarks: G.O. Sars described O. turgida from a few empty shells from 90-110 m in Lofoten, and mentioned that Jeffreys had some material of the same species from Finnmark donated by MacAndrews and Barrett (according to usage at the time, 1856, ‘Finmark’ might be anywhere in northern Norway). He listed the max. length as 3.2 mm, versus 5.0 for O. unidentata. A photograph of the holotype was kindly made at my request at the Natural History Museum, University of Oslo (Figure 56 at left). The condition of the shell is not good, but it may be deduced that the whorls of the spire are rather convex with a deeper suture than in O. unidentata and the body whorl is almost globose. Van Aartsen (1987) after having inspected the holotype considered that O. turgida was a synonym of O. unidentata. However, in my material some shells from northern Norway have a large, protruding protoconch and are definitely different from O. unidentata (cf. Figure 57 with Figure 66), and also different from O. conspicua, (which in Norway seems to be confined to the Skagerrak coast). These shells are most probably conspecific with O. turgida, although the body whorl is more keeled in my shells. The aperture is also somewhat more squarish in my shells. These differences might be due to size differences. Best distinguished from O. unidentata by the apical angle, the completely exposed protruding protoconch, and in well preserved shells, by the lack of three spiral striae at the base of the protoconch (as is found in O. unidentata, Figures 65 and 66).