make its appearance till the Oligocene and then only in America, the earliest European Dosinia being of Miocene date.” This apparent difference in age between American and European occurrences was due to differences of opinion as to the boundaries of the Oligocene and Miocene (Vaughan 1924, p. 727). In both countries Dosinia appears in the Aquitanian (Cossmann and Peyrot 1911, p. 405).

Von Ihering, however, claimed a much earlier appearance of the genus in the Southern Hemisphere (1907, p. 298), “Le genre n'est pas representé dans la craie des Indes, mais il a été trouvé dans la formation crétacée du Chili et de l'Argentine (Roca)…. Il faut done conclure que le genre Dosinia est un élément ancien des côtes antarctique de l'Archinotis.” As Stoliczka has pointed out that the Cretaceous records of Dosinia “are mostly not true Dosinias but belong to Cyprimeria and other groups” (Dall 1903, p. 1224) it would be interesting to know if the hinges of these South American shells have been clearly exposed. White (1888, p. 97, pl. 8, figs. 13, 14, 15) described and figured Dosinia brasiliensis from several localities in the Upper Cretaceous of Sergipe, Brazil. None of his figures shows the hinge, but the text describes the sublunular tooth as strong. If this is correct, the shell is certainly not a Cyprimeria.

Other Cretaceous records of Dosinia from Tunis and Portugal were given by Woods (1917, p. 32) in describing two unnamed “Dosinia sp.” from the Upper Senonian of Selwyn Rapids, New Zealand; but unfortunately these northern occurrences were not mentioned by Dall, Jukes-Browne or Cossmann and Peyrot, so the writer was unable to ascertain if the hinges had been examined. The teeth of three of the New Zealand specimens handled by Woods have now been partly cleared of their resistant matrix and the absence of an anterior lateral tooth is certain. They are described below as Cyclorismina woodsi n. gen., n. sp.

Dosinia, however, occurs long before the Aquitanian in New Zealand. It is true that no exact correlation of our strata with European stages is yet possible, but from the relative position of the beds in the Tertiary of New Zealand one can make a fair guess at their approximate age. Dosinia mackayi from the Bortonian of North Otago is certainly pre-Aquitanian, perhaps Upper Eocene, and Dosinia ongleyi from Wangaloa is still older, occurring in beds that have often been classed as Cretaceous but which are probably Paleocene.

After this paper was in the press, the writer noticed that the anterior tubercle in the left valve of Dosinia had arisen from an extension of the anterior cardinal. This may be seen clearly in the new subgenus Kereia, also in young stages of Dosinia lambata (Gould) and probably in young stages of many other species. It follows that the Dosiniinae are not closely related to the Meretricinae as generally supposed; but have been derived from such shells as the Cretaceous Cyprimeria and Cyclorisma. For further remarks on the significance of this tubercle see p. 598.

Although Dosinia is a common genus in the middle and later Tertiary of New Zealand, complete shells are difficult to collect, so that identifications have generally to be made either from specimens showing only the exterior or from fragments showing the hinge. The