Asteroceras marstonensis & Promicroceras planicosta.
This species of Asteroceras is only known from the famous Marston Magna Ammonite Marble Triangular piece of matrix plastered in beautifully preserved 3D Ammonites with original white shell preserved.
Jurassic, Upper Sinemurian, Obtusum Zone. 'Ammonite Marble'.
Marston Magna near Yeovil, Somerset.
Specimen : 8 x 5 x 3 cm.
