458 Transactions. 



The appearance of the grains under the microscope is that 

 of glauconite, not chlorite. They are rounded, and green- 

 coloured with a tinge of yellow, with a faint scarcely percep- 

 tible pleochroism. In a few of the sections examined the 

 mineral is seen filling the chambers of Cristellaria rotulata. 



Age of the Series. — All the species that are found fossil in 

 the district occur at the Miilburn quarry. They show that 

 this series should be correlated with the Oamaru formation.* 

 Out of tire thirty-five species which I determined at Miilburn, 

 thirty had been described from the Oamaru formation in other 

 districts. As to the geological age of this Oamaru formation, 

 opinions are divided. In 1850 Dr. Mantell, Professor Morris, 

 and Professor R. Jones considered it either Eocene or Upper 

 Cretaceous. In 1865 Dr. Hectorf considered it Miocene. In 



1865 Dr. Zittel and Dr. Stache considered the northern equi- 

 valents of this formation as Oligocene or Upper Eocene. In 



1866 Hector split up the formation, calling some Upper Plio- 

 cene, some Lower Pliocene, and some Miocene. In 1870 

 Hector! considered the Oamaru rocks as Upper Tertiary ; 

 the Waitaki, Tokomairiro, Caversham, and Wakatipu rocks as 

 Lower Tertiary. In 1871 Hector § placed the Oamaru forma- 

 tion as the closing member of his Cretaceo-tertiary system. 

 In 1872 Hutton considered the Waitaki and Wakatipu mem- 

 bers as Lower Oligocene, and the Oamaru, Caversham, &c, 

 members as Upper Eocene. In 1875 Hutton|| considered it 

 doubtful whether the Oamaru formation was Upper Eocene 

 or Lower Miocene, but he inclined to the latter belief on ac- 

 count of the presence of forms such as Carcharodon megalodon. 

 In 1879 Von Haast^I considered it Upper Eocene. In 1880 

 Hector** called it Upper Eocene, and has kept to that opinion 

 ever since. In 1885 Huttontf considered it Oligocene, and has 

 repeated that opinion. In 1902 ParkJJ referred it to the Upper 

 Eocene. 



The question of age thus seems to be narrowed down to an 

 issue between the closely allied Upper Eocene and Oligocene. 

 with high authority supporting each opinion. 



* Hutton, "Geology of Otago " (1875). p. 46. 



t Hector, Quart. Journ. Geol. Soc. (1865), vol. 4, p. 128. 

 t Hector. " Catalogue Colonial Museum " (1870). 

 § Hector, Trans. X.Z. Inst. (1871), vol. iv, p. 245. 

 'I Hutton, " Geology of Otago " (1875), p. 54. 



• Von Haast, "Geology of Canterbury and Westland" (1879), p. 315. 

 ** Hector, Preface to Tenison-Wood's " Corals and Bryozoa of New 



Zealand " (1880), iii ; " Outline of New Zealand Geology " (1886), p. 53. 



tf Hutton, Quart. Journ. Geol. Soc. (1885), vol.'xli. pp. 194, 206; 

 Trans. X.Z. Inst. (1899), vol. xxxii, p. 169. 



ii Park, Trans. X.Z. Inst. (1902), vol. xxxv, p. 393. 



