320 Br. P. Mnrsliall — Younger liock Series of Neic Zealand. 



members may be contracted or even absent wbile others may be 

 correspondingly expanded in accordance with local variations in the 

 conditions under which their accumulation took place. Eor instance, 

 the basal conglomerate is not more than 5 feet thick at Amuri Bluff, 

 wliile at Shag Point the least thickness that has been assigned to it 

 is 1,250 feet. South of Oamaru the grey marls are almost entirely 

 absent, while in the Wanganui Basin they are at least 2,000 feet 

 thick, and their deposition there extended throughout all later 

 Tertiary time. In localities adjacent to the old shore-line greensands 

 and limestones are practically absent. 



2. The very nature of the rock succession indicates continuous, 

 uniform, regional depression until after the deposition of the 

 limestone. Thereafter elevation commenced. 



3. As a result of this movement of a land surface previously much 

 eroded, the upper strata that were deposited widely overlap those that 

 were deposited earlier. 



4. As the shore-line retreated the districts where the basal 

 conglomerates were first deposited became deep-water areas, while 

 conglomerates were still forming on the sea margin which in con- 

 sequence of the depression had advanced far on to the old land 

 surface. The conglomerates in their different portions therefore 

 represent the various periods that elapsed during the progress of 

 the movement of depression. This consideration seems to me to 

 satisfactorily explain the association of faunas of different ages with 

 the conglomerates. When these basal beds are well known it is 

 reasonable to suppose that the complete development of the Tertiary 

 fauna will be revealed. 



5. The fact that conglomerates of different localities contain 

 different faunas does not indicate that two series of rocks are present, 

 but it is the necessary result of the accumulation of sediment on the 

 margin of a gradually retreating shore-line. 



6. The coal-seams are always found in the basal conglomerates 

 and associated beds, and may therefore belong to any of the periods 

 that elapsed during the movement of depression. Low-lying littoral 

 districts were constantly being converted into swampy areas where 

 vegetable matter would accumulate, and from this coal would after- 

 wai'ds be formed. Conditions favourable for the formation of coal 

 might occasionally recur during elevation ; but the vegetable matter 

 would then not usually be buried, and all superficial deposits would be 

 rapidly eroded. 



I hope that this brief resume sufficiently indicates the radical 

 difference between our explanation and that bused upon the Cretaceo- 

 Tertiary classification with which there is a tendencj" in some minds 

 to confuse it. The Cretaceo-Tertiary classification hypothecated three 

 separate periods of deposition separated by periods of elevation. It 

 placed practically all the coal-seams in the middle of these three 

 ])eriods and thus classed all of them as the same age. This latter 

 idea has now been abundantly disproved. 



I may say that although alone responsible for this reply to Professor 

 Park's criticism, it has been submitted to Messrs. Speight and Cotton, 

 and meets with their approval. 



