Odostomia umbilicaris ( Malm, 1861 )

Høisaeter, Tore, 2014, The Pyramidellidae (Gastropoda, Heterobranchia) of Norway and adjacent waters. A taxonomic review, Fauna norvegica 34, pp. 7-78 : 32

Odostomia umbilicaris ( Malm, 1861)

Figure 43-44

Turbonilla (Odontostomia) umbilicaris Malm , n.sp. – Malm, 1861:623

Odostomia umbilicaris (Malm) - Jeffreys 1867; Friele 1874; G.O. Sars 1878; Marshall 1899; Winckworth 1932; Høisaeter 1986; Fretter et al. 1986; Graham 1988

Odostomia acuta var. umbilicaris (Malm) - Smith & Heppell 1991

Ptychostomon umbilicare (Malm) - Kobelt 1903

Type material: Göteborg (?)

Type locality: Löken, Western Sweden (?)

Material seen: Norway - Skagerrak , 4 spms (tentative identification).

Diagnosis: Shell: Cyrtoconoid moderately sized shell. Convex whorls and deep suture. Large umbilicus. Partly submerged protoconch. Prominent columellar tooth. Soft parts: Not known. Operculum: Not known.

Biology: Not known, but reported by ( Malm 1861) together with Modiolus adriaticus on the Swedish west coast.

Distribution: According to Friele (1874) not rare at one of his localities, Biskopshavn, (in Bergen) 55- 75 m. Not recorded by Norman (1879) and a record in G.O. Sars (1878) is only a repetition of the one in Friele (1874). (The two shells depicted in Figure 44 are from Friele’s locality, Biskopshavn, and identified by him). This record of Friele seems to be the only one from Norwegian waters (Malm’s record from 150 fathoms, Eggers Bank is intractable). In my material, four specimens from the Skagerrak region, and probably several others listed as O. acuta (following van Aartsen 1987, see Remarks below). Outside Norway it is recorded from the Swedish west coast, the northern and western coasts of the British Isles and south west Ireland ( Jeffreys 1867, Marshall 1899b, Fretter et al. 1986). In all newer literature regarded as a synonym of O. acuta , following van Aartsen (1987).

Remarks: Authorship is usually attributed to ‘Malm, 1863’, but the species was briefly described already in Malm (1861). Van Aartsen (1987) expressed as his opinion that the O. umbilicaris described and figured by Jeffreys (1867) (at left in Figure 43), is a form of O. acuta . He ‘supports’ this opinion by showing photographs of Jeffreys’ ‘type’ of O. umbilicaris and a shell of O. acuta from his own collection. He states that “… these shells (to) differ only in its more shiny surface and its more convex whorls.” He could not compare his O. acuta with Malm’s unavailable type of O. umbilicaris however, so that there might still be doubts as to the identity of the two nominal species. I find that the differences between the two shells figured in van Aartsen (1987) are striking, and in the material I have seen they seem to be rather constant. Schander (1995) presents a photograph of what he calls O. acuta from the Koster area in western Sweden (centre in Figure 44). This has all the attributes of Jeffreys’ concept of O. umbilicaris , but Schander does not comment further on the relationship between O. acuta and O. umbilicaris . Both Jeffreys (1867) and Marshall (1899b) describe the distinction between these two species: “This species [ O. acuta ] may be distinguished from O. umbilicaris by its greater solidity, the periphery being always keeled, the spire much longer, and the whorls compressed instead of convex” ( Jeffreys 1867:132).”It [ O. umbilicaris ] is most like a stumpy O. acuta , but the latter is more solid and conical, the whorls less tumid and the last whorl smaller proportionally.” (Marshall 1899b:231). Fretter et al. (1986) regard O. umbilicaris to be the most easily identified of the British species of Odostomia , based on just those characters van Aartsen mentions. Fretter et al. do discuss an additional character, however, not mentioned by van Aartsen (1987), in spite of this character being regarded as the most important for distinguishing between a number of closely similar pyramidellids, viz. the inclination of the growth lines. This inclination is shown by Fretter et al. (1986) to be from 8 to 10 degrees for O. acuta , and from 24 to 33 degrees for O. umbilicaris . If these measurements are representative and correct, there is no possibility that the two are conspecific. Until living specimens are available for analyses, I regard it as prudent to regard the two as distinct and keep them apart in fauna lists.