308 Geology of 



jSTo. ■! — Gradually this tufa becomes harder, formed of 

 stratified layers of brown or dirty green colours, 

 alternating frequently with each other, and becom- 

 ing glauconitic towards the bottom ... ... about 20 f ee* 



No. 5 — Being underlaid by tufaceous calcareous sand- 

 stone ... ... ... ... ... ... „ 40 „ 



Gradually altering to — 



No. 6 — Calcareous greensands, becoming towards the 



centre almost black, from grains of glauconite ... ,, 30 ,,. 



No. 7 — The latter are cut off from the lowest beds by 

 several layers of shell limestone, consisting mostly 

 of fragments of shells, and enclosing specimens of 

 Pectunculus, of a small white Ostrea, and casts of 

 a bivalve (Mesodesma ?) ... ... ... ... ,, 10 ,, 



No. 8 — The lowest beds of the whole series are formed 

 of quartzose sands of light colours, and of con- 

 siderable thickness, which will be valuable for 

 glass-making. 



No. 8 reposes on the slopes of much decomposed quartziferous 

 porphyry. 



More towards the centre of the section, and near the channel 

 through which issued the submarine eruption, the beds 5 to 8 are 

 missing. Here repose directly upon the palaeozoic rocks, occurring as a 

 small outlier, thick beds of a tufaceous or agglomeratic character. In 

 some localities, such as the Two Brothers, they consist entirely of 

 palagonitetufa of an uniform texture, whilst a little nearer to the centre 

 of eruption the compact dark mass contains numerous fragments of the 

 same rock enclosed, but of a somewhat lighter colour. On the opposite 

 side of the river, at the base of Mount Somers, portions of the same- 

 beds are extensively developed, but only the higher series are exposed 

 to view. Of these, the district around the so-called Mount Somers 

 caves, amongst other localities, is the most conspicuous and well-known 

 example. The caves owe their formation to a small creek having 

 washed out its way at the junction of the beds Nos. 1 and 2. The 

 palagonite tufas are here the lowest beds visible. The calcareous beds 

 contain a number of fossils, connecting them with those of the Curiosity 

 Shop at the Bakaia. Another outlier of the same series, and proving 

 that these beds extended once over a considerable portion of the 



