116 Transactions. 



In 1916 Thomson proposed to divide the rocks exposed on the Wanganui 

 coast-line into the Castlecliffian and Waitotaran series. This proposal, 

 however, was not based on any further work, but merely on a consideration 

 of Park's work and of the lists of fossils that he had recorded. 



Murdoch (1900, p. 216) described further species that had been col 

 lected by himself and others from the blue clays in the Castlecliff area. 



All of the strata on the coast-line north of Wanganui, as far at least 

 as Patea, were placed by Hutton (1885, p. 211) in the Pliocene system. 

 Hecter (1886, p. 48) placed the strata partly in the Upper Miocene. 

 Park (1887, p. 57) placed the beds near Wanganui in the Upper Pliocene, 

 those at Nukumaru in the Lower Pliocene, and those between Waitotara 

 and Patea in the Upper Miocene. 



The present work was undertaken partly to discover the thickness of 

 the strata exposed on the coast-line, and partly to find out as accurately 

 as possible the extent to which the fauna changed as the depth in the 

 strata, and therefore the geological age, increased. At first the intention 

 was to collect the fossils in every stratum in which they could be found, 

 and to make a separate list of the fauna in every case. The great number 

 of fossil-bearing strata soon showed that such a project was impracticable, 

 and that for the present purpose it was also undesirable, for each single 

 stratum contains a small fauna only. If the fauna of each stratum were 

 taken separately there would result a very large number of lists, and the 

 comparison of these would lead to much confusion. For these reasons 

 four different collecting localities have been chosen, and in each instance 

 a thickness of about 500 ft. of sediment has been searched carefully, . and 

 as complete a collection as possible has been made from it. The lists that 

 have been made cannot in general be regarded as in any way exhaustive, 

 but in nearly every instance several visits have been made by two collectors 

 in company. The Castlecliff locality has probably been almost completely 

 collected, for much time has been spent in the study of the strata there, 

 because it is most accessible. The late S. H. Drew obtained a large 

 number of fossils there, and one of us has collected in these strata fox 

 a number of years, and of late times it is only rarely that any additions 

 have been made to previous lists. 



The localities that have been chosen as suitable for the comparison of 

 faunas are as follows : — 



{!.) Castlecliff. — A thickness of about 500 ft. of strata, commencing at 

 the southernmost end of the sea-cliff's and ending about a mile and a half 

 from the mouth of the Wanganui River. Nearly every stratum in this 

 thickness *is fossil-bearing. Almost all of the strata consist of a fine but 

 hard blue clay — the so-called " papa." The fineness and general nature of 

 this material, as well as the mollusca that it contains, give the impression 

 that the material was deposited on the floor of a sea that was not less than 

 50 fathoms in depth in this locality. As the strata are followed to the 

 north and rise in the cliffs the material becomes a little coarser, and often 

 changes to a micaceous sand before it works out at the top of the cliff. 

 This apparently indicates that the water became shallower in the northern 

 part of the district. This conclusion is supported by the nature of the 

 fossil mollusca which have been found in the sandy facies of the strata. 



(2.) Kai Iwi. — This locality is five miles to the north of the previous 

 one. The rocks which extend about a mile to the south of the Kai Iwi 

 Stream form the source of the collections classified under this name. 

 The material is almost entirely blue clay of a fine unctuous nature. The 

 collection that has been made is less complete than those made in the other 

 localities. 



