MEETINGS OF SOCIETIES. 14I 



that the fossil-species forming the bulk of the deposit had been derived 

 from an older deposit, either forming the bed of the lake or now 

 buried beneath the scoria hills to the east of Paoroa. But it seemed 

 to him that, in order to account for the facts of the case, it must be 

 supposed that at first only fossil-species carried along the underground 

 channels were deposited in the little basins whence the specimons 

 were obtained. And as the deposit was entirely composed of fossil- 

 species to within 1ft. of the present surface, the introduction or 

 appearance of living forms was of very recent date. As, however, the 

 whole deposit was manifestly of quite recent date, and as at first the 

 conditions were as fit for the existence of recent forms of diatoms as 

 they now were, it seemed extraordinary that throughout the deposit 

 there was not a mixture of fossil and living species. Taking these 

 facts into account, he (Mr. McKay) would prefer to account for the 

 difference -in the species found in the top and bottom beds of the 

 deposit, by supposing that the species first living in the pond gave 

 place to other forms, either modified descendants of the original 

 species or species introduced from different stocks, and in this way 

 would avoid the necessity of hypothecating an older deposit, the exis- 

 tence of which had not been proved, and, at the same time account 

 for the separateness of the living and extinct forms as they were 

 found in the higher and lower parts of the deposit. He would here 

 add that as the surface-layers were formed wholly of living forms, and 

 all were extinct at about 1ft. 6in. from the surface, it seemed reason- 

 able to suppose that at, say, 6ft. from the surface other and quite 

 distinct species might be found. And as Mr. Williams informed him, 

 he (Mr. Williams) dug into the deposit to a yet greater depth without 

 passing through it Other and quite distinct species, it was probable, 

 would be found in the first-named and lower parts of the deposits. 

 If samples were taken not more than 6in. apart in the section of the 

 deepest part of the deposit, an examination of these would be likely to 

 set at rest any doubts as to the true origin and mode of accumulation, 

 since it was mainly a derived and secondary deposit ; then from about 

 lft. from the surface to the greatest depth there should be little 

 variation of the specific forms ; while on the other hand, if the species 

 changed more than once, that would go far to prove the correctness 

 of his theory on the subject. 



Mr. Maskell said that as he had been referred to in Mr. McKay's 

 paper, it would be necessary for him to ask the writer's leave to add a 

 a short note for the Transactions, explaining Iris view of this rather 

 puzzling matter. He had no pretensions to a knowledge of geology ; 

 but it was possible that a micoscopist's observations might sometimes 

 come in useful as an aid to a geologist, and perhaps this was the case 

 in the present instance. Put very shortly, the point was this : When 

 Mr. McKay handed over to him some specimens of these diatomaceous 

 deposits, he was at once struck with three peculiarities in them. 

 First, the upper deposit evidently owed its greenish tinge to the 

 presence of endochrome in the diatoms, showing therefore that these 

 organisms were not only recent, but alive. Secondly, the lower 

 deposit, on the other hand, was not only pure white, from the absence 

 of any endochrome, but also remarkably and exceptionally clean and 

 clear from sand and dirt, having all the appearance of a perfectly 



