U. S. NATIONAL MUSEUM 



PROCEEDINGS. VOL. 86 PLATE 16 



1, Opercuh'-.oide! wiUcoxu (Heilprin), Tantoyiica formation, near Tantoyuca, X'eracruz (Tanioyuca type locality): 

 2, O. tuxpanemis (Thalmann), Tuxpam formation, lower Miocene, near Tuxpam, Veracruz; 3, 0. antiguensis 

 Vaughan and Cole, Meson formation, near Bustos, Veracruz (Bustos Well no. 1). X20. 



