Wednesday, 8 May 2019


Ilymatogyra arietina / Oyster Slab
Ilymatogyra arietina, Oyster Slab, Lower Cretaceous, Washita Division, Del Rio Formation, Williamson County near Georgetown, Texas, USA.

The highly calcareous siltstones of the Del Rio Formation at Washita have huge blocks of Ilymatogyra packed so tightly one specimen overlaps with the next. If you're in the area, it is well worth a field trip.