Fox. — The Waitemata Series. 471 



bursts were " most probably at the horizon of (the Parnell 

 grit and) the Takapuna ash-bed," 1 infer that they were those 

 species which are common to the Orakei greensand and the 

 Cheltenham breccia — very probably Pectens and Bryozoa. I 

 have not had an opportunity of examining the Waitakerei 

 breccias, but I am informed that immense numbers of Bryozoa 

 are found in them ; and this is the most striking and charac- 

 teristic feature of the Cheltenham breccia. 



A description has already been given of the Cheltenham 

 lava. Besides examining the slides of the Waitakerei lava in 

 the Auckland University College laboratory, I made several 

 mvself from lava in situ, and found the lava very similar to 

 that contained in the breccia. Naturally, all the outcrops of 

 the bed are not likely to owe their origin to the same vents, 

 since several vents along the chain were, no doubt, active 

 simultaneously. Where, however, we can ascertain approxi- 

 mately the position of the vent from which the materials of 

 the bed at any one outcrop were derived the lava in situ 

 shows a striking resemblance to the lava in the bed, which is 

 all we can expect. Till the Waitakerei eruptions have been 

 studied, more than a general similarity need not be looked 

 for. I may, however, give one case of more certainty, and 

 therefore more interest. 



The outcrop of the breccia at the White Bluff is not many 

 miles from the range, and is, moreover, at the southern end 

 of the chain, so that the southern vents may be considered as 

 its source. In the bed there are several varieties of lava, but 

 the commonest are — (1) A purple earthy rock with abundant 

 phenocrysts of kaolin ; (2) a black amygdaloidal rock with 

 bright unaltered feldspar phenocrysts ; (3) a dark-brown or 

 chocolate rock of a somewhat holocry.stalhne appearance 

 since the phenocrysts of feldspar are very numerous, and 

 large black phenocrysts of pyroxene also occur. These three 

 kinds of lava are found to be plentiful in situ in various 

 localities between Big and Little Muddy Creeks, about six 

 miles to the westward. 



The Waitakerei Range is, moreover, the only chain of 

 Oligocene vents near at hand, and the breccia cannot have 

 come from a distance. The size of the included fragments, 

 varying from 1ft. to 4 ft. in diameter, is, it seems to me, 

 conclusive. I have also found numbers of elliptical or round 

 volcanic bombs, which are not likely to have come a great 

 distance. The bed cannot often be seen in successive out- 

 crops, each nearer than the last to the Waitakerei Range, but 

 where this can be observed the nearer outcrops are always 

 the coarser. St. Helier's Bay, for instance, is about twice as 

 far from the vents as the White Bluff, and the coarseness at 

 the latter is much more marked than at the former spot. 



