Ordovician

[,ɔ:dəu'viʃən;-ʃiən]

Definition

(noun.) from 500 million to 425 million years ago; conodonts and ostracods and algae and seaweeds.

Typed by Carla--From WordNet

Definition

(a.) Of or pertaining to a division of the Silurian formation, corresponding in general to the Lower Silurian of most authors, exclusive of the Cambrian.

(n.) The Ordovician formation.

Editor: Vanessa