BY W. N. BENSON. 547 



considerable quantities. This is quite in accordance with the 

 results obtained by Prof. Skeats,* which show that up to fifteen 

 per cent, of magnesium carbonate may be absorbed by a lime- 

 stone before dolomite crystals appear. The question arises as to 

 the cause of the presence of so much magnesium carbonate in the 

 marble, Was it brought in by the metalliferous solutions, which 

 were rich in magnesia; or was it introduced by replacement from 

 sea- water while the limestone was still a coral-reef, after the 

 manner described by Prof. Skeats "? The latter I should imagine 

 to be the case, for if the magnesia were derived from silicate 

 solution it would probably be in accordance with an equation 

 like the following 



2CaCO;3 -t- MgSiOs = CaCOgMgCOg + CaSiOs 

 which would mean the formation of much wollastonite. Now, 

 though I have seen a specimen of wollastonite said to have come 

 from Caloola, I have not seen any in situ, and must hence believe 

 it to be rare. Therefore, the reaction above could not have 

 taken place on a large scale, and therefore the alternative origin 

 of magnesia in the marble must have been the more important. 



So far fossils have not been found in this quarry. 



ii. (Portion 66, Parish Lowrj'). This is a narrow lens, less 

 than three chains wide, crossing a small creek about three- 

 quarters of a mile south of Occurrence No. i. It is a very fine- 

 grained, good, solid marble, but its extent is not yet de6nitely 

 settled. Probably it extends only a chain or two north of the 

 creek, but may run further to the south. Major axis runs about 

 N.N.E. 



iii. (Portion 265, Parish of Ponsonby). This quarry, the first 

 one to be worked, is situated a mile to the S. S.W. of No. i. It 

 was originally worked for lime. The marble is of a rather finer 

 grain than the previous occurrences, and in the exposed portions 

 shows a pink or creamy colour. It is intersected by veins of 

 almost colourless, coarsely crj^stallised calcite. Sericite and 



'' Bull. Mus. Corap. Zool. Harvard Coll., Vol. xlii., p. 102 (1903). 



