Syntypes of Cyrenoida floridana and lectotype of C. guatemalensis. 1–4. Cyrenoida floridana (USNM 46846, length 12 mm, height 13 mm). 1. Left valve, external view; 2. Right valve, external view; 3. Left valve, internal view; 4. Right valve, internal view; 5–10. Cyrenoida guatemalensis (ANSP 107532; length 8.6 mm, height 8.9 mm). 5. Left valve, external view; 6. Right valve, external view; 7. Left valve, internal view; 8. Right valve, internal view; 9. Detail of left hinge; 10. Detail of right hinge. Scale bar: 2 mm.