Hirudocidaris uniformis essenensis (Schlüter, 1892)
This species from the Grey Chalk is unusually common in the coarse, sandy limestones of the SW, where complete tests are frequently found. Good material is much more scarce elsewhere in the UK. Primary spines are similar to certain forms of the related Hirudocidaris hirudo, but tend to have more prominent ribs, and are perhaps slightly more stout.
1). (A) Typical primary spine (x3.5, sandy facies of the Grey Chalk, S W England, Randell Collection, RR0646). (B) Adoral view of a well preserved test with some articulated primary spines and scrobicular spines (x2.5, near Cow Gap, Eastbourne (L. R. Strevens collection), Grey Chalk).
2). (A) Adoral, (B) lateral (side) and (C) adapical views of a complete test (x3, SW England (from an old collection), sandy facies of the Grey Chalk, Randell Collection, RR0136).