294 C. T. Trechmann — Cretaceous Mollusca 



1912. " Lamprophyre Dykes in Long Sleddale" : ibid., pp. 266-7. 

 1914. " Fractional Crystallization the Prime Factor in the Differentiation 

 of Rock-magmas " : Congr. Geol. Int. Comp.-Rend., xii, pp. 205-S. 

 "The Sgurr of Eigg : some Comments on Mr. Bailey's Paper": 



Geol. Mag., pp. 306-8. 

 " Some Remarks on Geology in Relation to the Exact Sciences, with 

 an Excursus on Geological Time " (Presidential Address to the 

 Yorkshire Geological Society) : Proc. Yorks. Geol. Soc. , vol. xix, 

 pp. 1-13. 



1916. "Differentiation in Intercrustal Magma- Basins" : Journ. Geol., 



vol. xxiv, pp. 554-8. 



1917. Presidential Address to the Geological Society of London, delivered 



February 16 (see Reports and Proceedings, Geol. Mag., pp. 191-2, 

 April, 1917). 



II. — Cretacicous Mollusca from New Zealand. 

 By C. T. Trechmann, M.Sc, F.G.S. 

 PLATES XIX AND XX. 1 

 Introduction. 



OWING to incomplete paheontological knowledge, the true age 

 and correlation of the various divisions of the great Mesozoic 

 series of New Zealand, which, together with the Maitai Series, forms 

 such an important element in the structure of the country, has long 

 remained a matter of uncertainty. In consequence the idea has to 

 some extent taken hold among New Zealand geologists that the 

 Mesozoic faunas, owing to supposed conditions of isolation, show 

 archaic features. It was explained that certain Permian forms 

 occurred in the Trias and that Trias forms may have persisted into 

 Jurassic times, and to a still greater extent that a Cretaceous fauna 

 lived on in this portion of the earth into the Tertiary period. 



On going further into these questions I find no support for the 

 theory, and in the case of the Cretaceous, a comparison of the fauna 

 of the Senonian with corresponding faunas of Australia and especially 

 of South America shows that the isolated survival theory is un- 

 tenable. The arguments adduced in its favour apply equally well to 

 the Cretaceous of South America and other parts of the Indo-Pacific 

 region as they do to New Zealand. 



It must be remembered that the present isolation of New Zealand 

 as a land mass is a phenomenon of late geological time. In the 

 Permo-Carboniferous period there was as much or more land in the 

 Southern Hemisphere as there now is in the Northern. The Cretaceous 

 and Tertiary faunas of New Zealand point to a much closer connexion 

 with South America than obtains at the present day. The number 

 of species of recent Mollusca common to the coasts of New Zealand 

 and Tierra del Fuego is now very slight. 



In a paper recently published in this Magazine 2 I showed that the 

 Maitai Series contains a fauna which agrees, so far as it goes, exactly 

 with that of the marine Permo-Carboniferous of New South "Wales 



1 Plate XXI will appear with the second part in the August Number. 



2 "The Age of the Maitai Series of New Zealand": Geol. Mag., N.S., 

 Dec. VI, Vol. IV, pp. 53-64, Feb. 1917. 



