It consists of the seven species in section Oncostylis that have cylindrical inflorescences.

These range in form from small shrubs to tall trees.

The leaves grow in either an alternate or whorled pattern, with various shape forms.

The Spicigerae inflorescence is held erect, subtended by a whorl of branchlets, and retains a regular pattern until anthesis.

It is therefore thought to be the oldest of the series, having developed before the onset of aridity in the Nullarbor Plain.