Holaster trecensis (Leymerie, 1824)
A common and moderately large irregular echinoid from the Grey Chalk. Sternotaxis plana is superficially similar but occurs in the Turonian and Coniacian of the White Chalk. Holaster nodulosus is very close to H. trecensis and differs only subtly - H. trecensis has taller sides and a slightly undercut periproct.
1). Holaster trecensis (x2, Grey Chalk, near Cow Gap, Eastbourne, Randell Collection, RR1328). (A) View of the apical (upper) surface. (B) View of the oral (under) surface. The opening towards the anterior (top of the image) is the peristome.
2). Holaster trecensis (x2, Grey Chalk, near Cow Gap, Eastbourne). (A) Anterior (front) view. Oysters are attached to the bottom left. The opening bottom centre is the peristome. (B) Posterior (rear) view. The central opening is the periproct.
3). Holaster trecensis (x1.5, Grey Chalk, near Cow Gap, Eastbourne). Lateral (side) view, anterior (front) to the left.