Thirty species of Cancellariidae in 11 genera from the Miocene Gatun Formation in the Panama Canal area, Caribbean Panama, are discussed including two species not represented by specimens suitable for formal description. The following 11 species are described as new: Cancellaria harzhauseri n. sp., Cancellaria mixta n. sp., Bivetiella dilatata n. sp., Euclia alacertata n. sp., Pyruclia tweedledum n. sp., Pyruclia tweedledee n. sp., Massyla toulai n. sp., Aphera aphrodite n. sp., Axelella cativa n. sp., Agatrix agathe n. sp., Ventrilia coatesi n. sp. This assemblage of cancellariids is very diverse and highly endemic, with 18 (60 percent) species found only in the Miocene Gatun Formation. These assemblages all lie within the Gatunian Neogene Paciphile Molluscan Unit 1 (GNPMU1).