394: Transactions. 



The Saurian beds contain Plesiosaurus and other reptilian remains of a 

 Cretaceous facies, and are probably of Senonian age. According to Haast,* 

 the glauconitic greensands contain Waldheimia lenticularis (which he says 

 is also common in the Mount Brown beds), a Pecten, and a large smooth 

 Inoceramus which he says resembles Inoceramus flanus of Europe. When 

 Lima laevigata was first reportedf in the Cobden limestone it was called 

 Inoceramus. The presence of the brachiopods and pectens inclines me to 

 suspect that the large smooth Inoceramus of Haast may be, after all, nothing 

 more than Lima laevigata Hutton. 



The upper five members of the succession — or, at any rate, the upper 

 four members and the uppermost portion of the fifth (Amuri limestone)- — 

 are acknowledged by all to be Tertiary. The age of the glauconitic green- 

 sands has been considered Cretaceous by all who have written on this sub- 

 ject, but in view of the recent discovery of an assemblage of Oamaruian 



molluscs in tuffs intercalated in the Amuri limestone, and the doubt as to 

 • ... 



the correctness of Haast's identification of Inoceramus, I am inclined to 

 think that this view may have to be revised. 



The opponents of the Cretaceo-Tertiary hypothesis place the. uncon- 

 formity between the Cretaceous and Tertiary at the close of the Amuri 

 limestone. The discovery of Tertiary molluscs in the tuffs intercalated in 

 the Amuri limestone leads me to conclude that the unconformity must 

 be looked for under the Amuri limestone. Later investigation may even 

 show that the unconformity occurs between the Saurian beds and the 

 glauconitic greensands. 



The unconformities that have been recognized between the Mount 

 Brown and Greta beds, and between the Amuri limestone and Weka Pass 

 stone, may prove to be local and of no palaeontological significance. 



A glauconitic sandstone containing a Tertiary molluscous fauna has 

 been reported by McKay as lying below the hydraulic limestone at Kawa- 

 kawa, and a rich assemblage of molluscs was discovered by myselff as 

 far back as 1885 in glauconitic greensands underlying the hydraulic lime- 

 stone at Pahi, in the Kaipara district. The Pahi molluscs are undoubtedly 

 Oamaruian. The presence of this Tertiary fauna below the hydraulic lime- 

 stone has always presented one of the perplexing problems of the geology 

 of North Auckland. The correlation of the Amuri limestone with the 

 hydraulic limestone receives powerful support, from the discovery of a 

 Tertiary fauna in the Amuri limestone at the Trelissick Basin. The placing of 

 the Amuri limestone in the Tertiary succession removes the most perplexing 

 difficulty that has confronted geologists in the interpretation of the geology 

 of the North Auckland district. What now remains to be done is to determine 

 the relationship of the glauconitic greensands in the Middle Waipara to the 

 overlying Amuri limestone and the underlying Saurian beds. 



* J. Haast, Notes on the Geology of the Central Portion of the Alps, including 

 Mount Cook, Reports of Geological Explorations during 1870-71. 1871, pp. 11, 12. 



f A. McKay, Reports relative to Collections of Fossils made on the West 

 Coast District, South Island, Reports of Geological Explorations during 1873-74, 1877. 

 pp. 80, 101 ; and during 1874-76, 1877, p. 38. 



f J. Park, On the Kaipara District, Reports of Geological Explorations during- 

 1885, 1886, pp. 164-70. 



