Crested Oysters

These shells appear to be Crested Oysters or Ostrea equestris (Say, 1834).  One has group of barnacles attached to it.

They were found by a 17 year old Lucien Pearson Beckner in 1889 at Naples, Florida, USA. Mr. Beckner was a mentor to Professor James Conkin (1924-2017) and his natural history collection was left to him upon his death.