306 Transactions, — Geology. 



the fossils found in the series will bear out this classification. 

 How the pumice band came to be deposited among marl-clays 

 over such a vast area, and quite conformably to the underlying 

 and overlying beds, I am at a loss to explain. I venture, however, 

 to offer a suggestion. Are the blue-clays so common through- 

 out the district simply volcanic ejectamenta, which have been 

 subsequently acted on by aqueous agencies ? I am inclined to 

 think so. The blue-grey mud ejected from Rotomahana Lake 

 at the time of the Tarawera eruption, last year, bears a close 

 resemblance to the blue marl-clays in which the pumice band is 

 found. Those who have been over the volcanic district of this 

 island will readily understand that the eruption of mud from 

 Rotomahana is only one of many similar eruptions which have 

 taken place. Hot- water action and steam have played in the 

 past, as they still play, an important part in what is understood 

 as volcanic phenomena. The mixture of clay and pumice-grit and 

 pebbles, of which such a large proportion of the rocks between 

 Mahia and Tologa Bay are seen to be composed, suggests an 

 inquiry as to how a mixture of this sort came about. Clay, 

 equally with pumice, must be set down as a volcanic product ; 

 and I see no way to account for a conformity between the 

 pumice and clays, except on some such supposition as stated 

 above. The moya of the Central and South Amerian volcanoes 

 is the mud of the Tarawera eruption ; and we may suppose that 

 eruptions of mud have been no uncommon event in the history 

 of volcanic phenomena in this island. At least, such is my 

 opinion, and such is the suggestion I offer, as accounting for the 

 pumice band found in the rocks of this East Coast District, and 

 which are classed by the Geological Department as belonging 

 to the Cretaceo-tertiary formation. 



The accompanying map (Plate XVIII.) contains all the places 

 mentioned in this paper. 



Art. XL. — Notes on the Volcanic Rocks of the Taupo District and 



King Country. 



By Professor A. P. W. Thomas, M.A., F.L.S. 

 [Read before the Auckland Institute, litli November, 1887.] 



Mr. Cussen has requested me to identify for him a large number 

 of rock specimens collected during his stay in the Taupo District 

 and the King Country ; and the present notes are intended to 

 illustrate the more interesting points in connection with some 

 of them. 



Hochstetter travelled through the Taupo District in April, 

 1859, but his time there was limited, and gave little leisure for 

 the exploration of the country. He states that all the volcanic 



