Abstract
Concretions collected from Motunau and Glenafric Beaches, North Canterbury, New Zealand, have yielded a new genus and species of crab, Tongapapaka motunauensis of the xanthoid family Pseudoziidae and several specimens of the cancrid crab Metacarcinus novaezelandiae (Jacquinot in Jacquinot and Lucas), confirming its range from Miocene to Holocene. These beaches have yielded numerous specimens of decapod crustaceans, the lobsters and crabs, over the decades, and the composition of the decapod fauna suggests an offshore setting for the Greta Siltstone and Mt Brown Formation exposed at Motunau and Glenafric Beaches, respectively.