A very rare species belonging to the Echinothuroids.  The plates of the fragile test were bound only by collagen in life and rapidly collapsed after death.  Consequently, specimens are only very rarely preserved articulated.  Complete primary spines end in a 'hoof'.

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1).  Exceptionally preserved specimens with articulated and moderately intact tests; (A) Adapical view of a test encased in flint (x1.7, 'Senonian', White Chalk, BMNH (British Museum (Natural History) London) E1927; (B) Adoral view of the lectotype - a unique specimen with an articulated lantern protruding from the peristome (x2.0, Seaford Chalk, Charlton, Kent, BMNH 40240.  Images  © 2008 The Natural History Museum, by kind permission.

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2).  Articulated segments of the adapical surface of the test; (A) Paralectotype (x2.3, 'Senonian', Higham, near Rochester, BMNH (British Museum (Natural History) London) 40376; (B) Segment with an ambulacral column and partial apical disc (x3.0, Seaford Chalk, Gillingham, Kent, BMNH 82389.  Images  © 2008 The Natural History Museum, by kind permission.

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3).  Details of the lectotype in figure 1B, showing the unique, intact, articulated and three-dimensional Aristotle's lantern; (A) Adoral view, exhibiting peristomal plating around the lantern (x4.0); (B) Lateral view (x5.0).  Images  © 2008 The Natural History Museum, by kind permission.      

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4).  Adoral surface of a partial & flattened test (Kent, BMNH (British Museum (Natural History) London) 56833); (A) Overview of the specimen (x1.2); (B) Detail of the peristomal area showing the exceptionally preserved peristomal plating (x2.4).  Images  © 2008 The Natural History Museum, by kind permission.