Marshall. — Geology of the Centred Kaipara. 443 



After a great thickness of sediment had been accumulated on this sea- 

 floor a further movement of depress on of an important nature took place, 

 and a bed of Globigerina ooze of great thickness was formed. The depth of 

 the water increased to such an extent that over the calcareous matter there 

 was formed a stratum of diatomaceous and radiolarian ooze. When eleva- 

 tion took place again it appears that conditions were unfavourable to the 

 life of Globigerina, and the diatomaceous ooze is succeeded directly by a 

 fine white mudstone composed almost entirely of minute rounded particles 

 of quartz. It is extremely difficult to suggest the exact origin of this 

 material. The well-rounded form of the quartz certainly leads to the belief 

 that the deposit was of aeolian origin. It may be of the same nature as 

 the white clay, or white clay with ooze, now covering the sea-floor fifty miles 

 distant from Cape Maria van Diemen on the western side of the North 

 Island. There appears to have been very little life on the sea-floor at this 

 time. 



The elevation of the sea-floor continued gradually, and the deposit 

 became marly. A varied molluscan fauna then appeared, and at the same 

 time simple flabelloid corals and an abundant Miogypsina life. Volcanic 

 action took place on many occasions. Volcanic glass is found in the hard 

 limestone near Pahi. Marahenm Hill is formed of volcanic rock due to 

 submarine activity, and, lastly, there are the great beds of tuff and the lava 

 rocks at Komiti and on the south-east side of the Funnel. Further evidence 

 of submarine volcanic activity is found in the large beds of tuff and breccia 

 at Wayby and near Kaiwaka, where in the rock used for the railway ballast 

 specimens of A mphistegina were found in microscopical preparations. Lastly, 

 there is a small cone near Port Albeit. The volcrnic rock heie is quite 

 glassy, and though distinct proof was not found it seems that this material 

 also was formed by submarine eruption. 



PALAEONTOLOGY. 



The following rocks were found to contain fossils : (1) The gritty lime- 

 stone at Gibraltar Rocks, and bands of similar material between that 

 point and Pahi ; (2) the hydraulic limestones ; (3) the greensands near 

 Pahi ; (4) the mudstones with concretions near Batley, or ammonite beds ; 

 (5) the sandy and tufaceous beds near Pakaurangi Point. The gritty 

 limestones of the Gibraltar Rocks have been described previously. The 

 following genera of Foraminifera are represented : Carpenteria, Globigerina, 

 Rotalia, and Amphistegina. No specific determinations were possible. In the 

 absence of specific identifications it is not possible to state the exact horizon 

 to which the limestone belongs, though the presence of abundant Amphi- 

 stegina appears to point to the Miocene age. The same remarks apply to 

 all the other bands of grittv limestone between tdie Gibraltar Rocks and 

 Pahi. 



The Ammoxite Beds. 



These marly beds contain relatively few fossils, though those that have 

 been found have a peculiar interest. Up to the present time only five 

 species have been discovered, and three of these are, ammonites. 



Kossmaticeras de Groussouvre, 1901. 



This genus was established to include species derived from Pusozia and 

 Uhligella which show a close similarity to Holcodiscus, though these types 

 are supposed to owe their resemblance to phylogenetic convergence. 



