The shell has more rounded whorls, with a less trapezoidal aperture; the outer lip is much more arcuate; the apical and basal keels are weaker, and do not show these kinds of nodosities that arise at the intersections of these keels with the transverse lamellae on ammoniformis. Above and below: a shell heavily repaired shell, dredged in sediments at 600m deep, 10 mi off Dubrovnik, S. Croatia. 1,12mm. Original pictures provided by R. Stanić (HR) – (CC BY-NC-SA).

« …suture narrow but excavated; mouth horseshoe-shaped, with a thin edge, and expanding outwards; umbilicus very wide and open, completely exposing the spire on each side. » – J. G. Jeffreys: “On the Mollusca procured during the ‘Lightning’ and ‘Porcupine’ expeditions 1868-70 (Part VII)”, Proceedings of the Zoological Society of London for the year 1884, p.129.