Hurron.—On the Pareora and. Ahuriri Formations. 593 
then, we have a reason quite sufficient, apparently, to account for the 
difference between the fossils of the two formations; but we still have to 
account for the calcareous rocks of Lyndon, Mount Cookson, and Mount 
Caverhill having been classed with the clays of the Pareora formation, 
rather than with the calcareous rocks of the Ahuriri formation. Only 
nineteen species of shells are known from these localities. Of these eight 
are common to both the Ahuriri and Pareora formations in other localities, 
nine are found only in the Pareora or Wanganui formations, while two are 
found only in the Ahuriri formation. We thus see that, while the fossils of 
these localities are more nearly related to those of the Pareora than to 
those of the Ahuriri formation, still the percentage of species common to 
both is above the average. The percentage, however, is nearly the same 
at Motanau, and even equal to it at Napier, so that this explanation is not 
altogether satisfactory. 
But although neither difference of habitat nor difference of station 
appear to be quite capable of explaining the great difference between the 
fossils of the Ahuriri and Pareora formations, I think that the objections 
that can be urged against them are of little weight in comparison with the 
almost identical percentage of extinct forms in both, and it will be better to 
eonsider both formations as one until decisive proof can be got to the con- 
trary. When the geology of the Wellington district is better known, proof 
one way or the other wilt probably be obtained ; for the rocks in the Mana- 
watu Gorge and the Upper Wanganui belong probably to the Pareora 
formation, while those on the East Coast and also at Waitotara belong to 
the Ahuriri formation. 
Dr. Hector, in his recently published Geological Sketch Map of New 
Zealand, places his Kanieri series with the Hawke Bay series, and in this 
I think he is right; but he places the Awatere series with the Wanganui 
series of Shakespeare Cliff, and this I cannot agree to; for the fossils of the 
Awatere series are closely related to those from Motanau and Kanieri, and 
only 424 per cent. of them are recent, while the fossils from Shakespeare 
Cliff are very distinct, and 754 per cent. of them are recent. 
Art. XCII.—Descriptions of some new Tertiary Mollusca from Canterbury. 
By Captain F. W. Hurron, Director of the Otago Museum. 
[Read before the Otago Institute, September 5th, 1876.] 
Lasr year Dr. J. von Haast sent a collection of Canterbury tertiary fossils 
to the Otago Museum, with the request that I would describe the new 
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