Brachystomia angusta ( Jeffreys, 1867 )

Høisaeter, Tore, 2014, The Pyramidellidae (Gastropoda, Heterobranchia) of Norway and adjacent waters. A taxonomic review, Fauna norvegica 34, pp. 7-78 : 25-26

Brachystomia angusta ( Jeffreys, 1867)

Figure 27

Odostomia pallida var angusta Jefffeys, 1867:125

Odostomia pallida var angusta Jeffreys - Marshall 1899b ; Warén 1980

Odostomia angusta Jeffreys - van Aartsen 1987; Smith & Heppell 1991; Peñas et al. 1996; Schander et al. 2003; Høisaeter 2009

Type material: Syntype, Bantry Bay, USNM 132101 ( Warén 1980: 37, pl. 6, Figure 18 (not 22 as stated in the caption, van Aartsen 1987).

Type locality: Not designated ( Warén 1980)

Material seen: Norway - Skagerrak , 5 spms, 2 shs ; Møre og Romsdal 2 spms; Nord-Trøndelag, 6 shs; Nordland, 1 sh. All identifications are tentative .

Diagnosis: Shell: Similar to B. eulimoides , but narrower, and with orthocline growth lines. The body whorl occupies a proportionally smaller part of the shell than in B. eulimoides . From B. scalaris it is most easily distinguished by its less turreted form, with shallower sutures, especially the first few postnuclear whorls. Max. length given as 3.2 mm in Peñas et al. (1996). Soft parts: Not known. Operculum: Not known.

Biology: Not known.

Distribution: This species (or variety) has so far not been reported from Norwegian waters, but the localities listed by Jeffreys (1867:125, from Guernsey to Shetland), makes it likely that it should also be found in our waters. I have tentatively identified two specimens and ten shells as this species, all taken between 62°28’N and 67°15’N. Outside Norway it is only known from the localities mentioned by Jeffreys (1867) and Marshall (1899b) (“several places from Guernsey to Shetland, but rare”), the Atlantic coast of Spain ( Schander et al. 2003) and from the western Mediterranean ( Peñas et al. 1996). Van Aartsen et al. (1998) extend the distribution to Mauritania, Canary Islands and Cape Verde Islands. Van Aartsen (1987) states only that “ Od. angusta occurs in the Atlantic as well as in the Mediterranean.”

Remarks: The first author elevating this to a full species appears to be van Aartsen (1987), who separated it from the similar looking B. eulimoides , for which it has always been regarded as a variety ( Jeffreys 1867, Marshall 1899b). Later it has been accepted by Peñas et al. (1996) and Schander et al. (2003). My source for identifying this species is the photograph in van Aartsen (1987), showing a shell much like B. eulimoides , but somewhat narrower. The main character van Aartsen mentions for distinguishing the two is that B. eulimoides have clearly prosocline growth-lines, while those of B. angusta are more or less vertical. This distinction is only easily visible on very fresh material. To distinguish it from B. scalaris , which is also stated to have orthocline growth-lines, he notes that it has a H/W ratio>2, (against <2), and a shell shape like a slender oval (as against a shell of rissoid type). Further studies are needed for verifying that this is really a species belonging in the Norwegian fauna.