Coelostylina, Kittl, 1894

Coelostylina View in CoL ? sp2.

( Figs 70–71 View Figs 51–71 )

Material – Two fragmentary specimens (GBA 2019/009/0045–46) from boxes, labelled as Chemnitzia sp.

Measurements – The figured one (GBA 2019/009/0045), D = 16.6 mm, spiral angle: ~20°.

Description – Last three whorls represent the figured specimen. They are remnants of a rather highly turriculate shell, consisting of moderately convex whorls with a narrow and shallow concavity along the adapical suture; top of the convexity lies nearer to the abapical suture. The suture itself is in a slightly impressed position and appears as a groove. In the latest growth phase, the convexity of the whorl surface enfeebles into almost flat. Concomitantly, the periphery shifts from the line of maximum convexity to the line in prolongation of the suture where a weak angulation also develops. The base is subconoidal with convex wall; no trace of an umbilicus is found. No intact part of the peristome is preserved; the shell cross-section in this area indicates an axially elongated aperture/peristome without siphonal outlet.

The last two whorls bear an ornament of obscure spiral threads; they are denser in a belt at the midwhorl and sparser abapically from the formerly mentioned ones. On the last whorl, a strong thread follows the angulation. Pieces of sharp cords are also visible in the periaxial area on the base. Growth lines are observable only on the last whorl; they are slightly prosocline and opisthocyrt between the suture and the periphery, and seem to be slightly prosocyrt and nearly orthocline on the base.

Occurrence – Within Sinemurian to lowermost Pliensbachian (Lower Jurassic) part of the Hierlatz Limestone Formation in Hierlatz Alpe, Hallstatt, Austria.