The imbricating plates are strongly carinate medially, and are reduced in height, extending only partly up the shell wall.

[1]: 82  The ovigerous structures, as folds (branchiae) or finger-like projections (frenae) are tissues to which fertilized eggs adhere to incubate.

The maximum observed geographic range of Catomerus is from New South Wales to Western Australia, and Tasmania, where it mostly inhabits the northern coast.

Within this range, occurrences are not continuous, and apparently constrained by temperature, substrate preference, and wave action.

[6]: 20 [1]: 82 Catomerus prefers warm temperate seas, and breeds mainly during the austral winter, at temperatures ranging from 14 °C to 17 °C, and sublittoral to lower eulittoral water depths.