Marshall. — Tertiary MoUuscan Fauna of Pakaurangi Point. 277 



our fauna during Tertiary times. On the other hand, it is clear that 

 many genera have become extinct. It is also the case that many of the 

 genera that were in earlier times well represented have but few species 

 in the present fauna. Those that have become extinct include Cymbiola, 

 Niso, Cypraea, Trivia, Conus, Latirus, Erato, Cerithium, Cardium, Exilia, 

 Cucullaea. More generally it may be said that of the 205 genera mentioned 

 in Mr. Suter's Hand-list of New Zealand Tertiary Mollusca (1915) some 

 forty-eight are now extinct. This statement, however, does not give a com- 

 plete idea of the magnitude of the change that has taken place. Many 

 of the genera that in Tertiary times contained a large number of species are 

 now reduced to a very small number. Of these, Epitonium, Surcula, Tunis, 

 Siphonalia, Struthiolaria, Mangilia, Pecten, and Polinices are the most 

 prominent examples. 



In this comparison the purely littoral fauna cannot be properly con- 

 sidered, as remains of such organisms are so seldom preserved. No one 

 Tertiary horizon which has had its Mollusca properly collected and described 

 shows any notable introduction of species or genera which are absent from 

 lower horizons. Such facts go far to support the idea of a continuous isola- 

 tion of New Zealand throughout Tertiary times — a contention that has been 

 previously urged by the author on purely stratigraphical grounds. This 

 position has lately been supported by Thomson and Morgan, though 

 stated in a different manner : " Each Tertiary fauna seems to merge 

 gradually into the succeeding one."* Mr. Suter also has written to me 

 as follows : " There is no doubt that our molluscan fauna has greatly 

 decreased, and also that the Tertiary forms gradually merge into one 

 another." These statements appear to me to afford the strongest support 

 from the palaeontological standpoint to the view so frequently urged by 

 me that there is no important break in the succession of Tertiary sediments 

 in New Zealand. In the absence of satisfactory palaeontological material 

 in the past this view has been based on stratigraphical material, and it is 

 satisfactory to note that as the palaeontological material gradually accu- 

 mulates its verity is placed practically beyond doubt. jf^F" 



It is to be hoped that a complete comparison may be possible ere long 

 between our Tertiary faunas and those of Australia, South America, and 

 North America. In the meantime one can only emphasize the well-known 

 fact that our Tertiary fauna closely resembles that of South America, wheie 

 the species of Turritella, Malletia, Struthiolaria, Epitonium, and Polinices 

 are evidently extremely closely related to ours. Again, the occurrence of 

 the genera Perissolax and Heteroterma in the Wangaloa beds shows a rather 

 unexpected relationship between our earliest Tertiary beds and those of 

 the Tejon and Martinez districts in California. 



In New Zealand I have frequently stated that there does not appear 

 to be any stratigraphical discordance between the Upper Cretaceous 

 (Senonian) and the Tertiary horizons. In all known cases, however, deep- 

 sea beds of Globigerina or diatomaceous or radiolarian ooze intervene between 

 the Senonian and Tertiary horizons. In South America Wilckens, as 

 previously pointed out, has insisted on an important break between the 

 Senonian and the Miocene. Other authorities on the South American 

 stratigraphy hold very different opinions. The latest that I have seen is 

 that of von Ihering, who maintains emphatically that there is no break 

 between the Cretaceous and Tertiary : " Uberblicken wir die von uns 



* Preface to Palaeontolocjiral Bulletin No. 5, 191' 



