Cymblllaria carinata n.sp.

PI. 1 fig. 4

Description. Shell very small with rather thick, biconvex lenticular form, isostrophic and smooth with an acute keel at periphery; umbilici closed on both sides by last whorl. Aperture with a deep angular sinus culminating at the periphery in a long narrow slit; lips thick.

Dimensions. Holotype (F78343) MD 2.3 mm, TS 1.8 mm

Types. Holotype (F78343) and 10 paratypes (F78530).

Type locality. About 250 m west of Babbinboon Lane, in Swains Gully, 15 km south-west of Somerton, NSW (Locality 25).

Stratigrapbic position. In bioclastic limestone, 130 m above the base of the Namoi Formation.

Additional material. 3 specimens from 'Marohn' (Locality 28).

Geograpbic distribution. From Swains Gully to 'Marohn'.

Geological age. Middle to late Tournaisian.

Etymology. Derived from the Latin carina meaning carinate; referring to the spiral ridge at the periphery.

Remarks. This is a relatively rare species, and is characterised by a smooth biconvex shell with a long slit and peripheral keel. The specimens are similar to the type species Cymbularia galeata Koken in having a smooth convolute spire with a long narrow slit, but differs in that C. galeata has an asymmetrical adult shell and in lacking a keel on the periphery.