Tylocidaris (Tylocidaris) velifera (Agassiz & Desor, 1846)
Short, stout, club-like spines, restricted to the Grey Chalk Subgroup. Similar to the closely related Tylocidaris clavigera, but T. clavigera is exclusively from the White Chalk Subgroup. Also, the ornament on primary spines of T. clavigera tends to be arranged into much more highly defined vertical rows.
1). Isolated primary spine of Tylocidaris velifera (x10, Cow Gap, near Eastbourne, Randell Collection, RR1686).