Asteroceras sp.
A single aptychus on matrix. The aptychus (pleural Apthchi) are like a pair of doors that close off the termination of the body chamber when the soft bodied animal retreats inside its shell. They are usually composed of Aragonite rather than Calcite and so are rarely found with the Ammonite itself.
Jurassic, Upper Sinemurian, Obtusum Zone.
Black Ven, Charmouth / Lyme Regis, Dorset.
Apthychus : 1.5 x 1.1 cm.
