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Transactions. 



Owing to the fact that so few brachiopods are recorded from the 

 Waiarekan and the Awamoan elsewhere, the percentage of records of the 

 Waipara species from the various Oamaruian stages, though favouring the 

 correlation of the main Mount Brown limestone with the Hutchinsonian, 

 is little more conclusive than in the case of the molluscs. It is shown in 

 the following table : — 



Table VIII. 



1. Main Mount Brown limestone (D). 



2. Uppermost Mount Brown beds. 



When the affinities of the species not recorded elsewhere are taken into 

 consideration, the case for the correlation of the main Mount Brown lime- 

 stone with the Hutchinsonian, and for the uppermost Mount Brown beds 

 with the Awamoan, becomes much stronger. The fauna of the former 

 horizon consists entirely of species closely related to Hutchinsonian forms, 

 with the exception only of Bouchardia minima, known elsewhere Only from 

 the Ototaran, and Magadina hrowni, not known in the southern Oamaruian 

 localities. The fauna of the uppermost Mount Brown beds contains 

 characteristic large species, not easily overlooked, which are absent from 

 the southern Oamaruian localities- — viz., Stethothyris suffiata, Neothyris novara, 

 N. iheringi, and N. anceps — suggesting that either this horizon is unrepre- 

 sented at Oamaru, or that it does not there yield brachiopods, which is 

 the case with the Awamoan, while the Hutchinsonian affinities of part of 

 the remainder, mainly Rhizothyris, are offset by the Wanganuian affinities 

 of another part, Hemithyris and Neothyris. 



The species of Rhizothyris and Pachymagas which range from the main 

 Momit Brown limestone into the overlying beds consist for the most part 

 of- species not so advanced as regards elongation and folding as those 

 confined to the main limestone. The explanation seems to be that the 

 more primitive stocks had a longer range, while the more highly evolved 

 forms, possessing no further potentialities of evolution, were narrowly 

 restricted in time. The occurrence of the two species Rhizothyris elongata 

 and Pachymagas ;;:)arA;^ only in the Hutchinson Qiiarry greensand and in 

 the main Mount Brown limestone would of itself favour the correlation 

 of these two beds, but when the advanced nature of their evolution is 

 taken into account it enormously strengthens the case for the correlation. 

 Combining all three points of view, we may conclude that the evidence is 

 sufficiently strong to sujjport definitely the correlation of the main Mount 

 Brown limestone with the Hutchinsonian and of the uppermost beds with 

 the Awamoan. The evidence of the brachiopods as to the correlation of 

 the beds below the main limestone is inconclusive. 



Combining all lines of evidence, we find the following correlations 

 indicated : — 



Uppermost Mount Brown beds — Awamoan. 



Main Mount Brown limestone — Hutchinsonian. 



Lower Momit Brown beds — Ototaran. 



" Grey marls " and Weka Pass stone — Waiarekan. 



