This small echinoid is a very common and important zone fossil in the Early Campanian. Both the shape and adult size of this species vary stratigraphically, and therefore lends itself well to biostratigraphy (i.e. the various forms can be used to recognise specific horizons in the Chalk).
A B C
1). Offaster pilula (x4.5, Newhaven Chalk Formation, Peacehaven, Randell Collection, RR0407). (A) Apical (upper) surface, anterior (front) end at the bottom of the image. (B) Lateral (side) view, anterior end at left of image. (C) Oral (under) surface, anterior end at the top of the image. The opening is the peristome: a flexible plated surface in life, which encloses the mouth-opening.
2). Offaster pilula (x4.5, Newhaven Chalk Formation, Peacehaven, Randell Collection, RR0407).(A) Anterior (front) view. The opening bottom centre is the peristome. (B) Posterior (rear) view. The central opening is the periproct: a flexible plated surface in life which encloses the opening for the anus.