Hutton. — The Wanganui System. 345 



the relative ages of any two sets of beds belonging to the same 

 biological province. But it does not follow that this method 

 can be trusted for correlating with accuracy sets of beds in 

 widely distant areas. On the contrary, different districts have 

 undergone different physical changes, and we have therefore 

 every reason to suppose that alterations in floras and faunas 

 would proceed with unequal rapidity in different parts of the 

 world. At the same time, as the replacement of a whole marine 

 fauna can rarely be sudden, it follows that the percentage system 

 has some value even here. But it must always be used in con- 

 junction with a comparison of the specific forms of the two 

 areas. And here, again, it is only the wide ranging oceanic, or 

 deep sea species — such as sharks, cephalopods, and a few bi- 

 valves — which should be depended upon for evidence, but these 

 wide ranging forms are of the very greatest value in correlating 

 strata all over the world. 



In the present case we have no wide ranging species that 

 can help us in determiniug the European equivalent of the 

 Wanganui system, and the percentage of recent species is our 

 only resource. All geologists, however, would, I think, allow 

 that it belongs to pliocene, the only question being : to what 

 part of the pliocene should it be referred ? and this may be left 

 for the present undecided. Excluding the Kaimatera beds there 

 are 278 species of mollusca known from the system, and of 

 these 63 per cent, only are recent. This percentage is, how- 

 ever, likely to be increased, as many of the supposed extinct 

 species are minute, and may have been overlooked as living 

 forms. The reason the percentage of recent species is less in 

 the whole system than in any of its separate series or beds, is 

 that the recent species are more abundant individually, and 

 more widely distributed, than the extinct forms, which are 

 usually rare and local. The following genera, found in the 

 Wanganui system, are not known to live in the seas of New 

 Zealand : — Ringicida, Oliva, Sigaretus, Eulima, Eulimella, Ad- 

 mete, Cerithium, Risella, Lutraria, Loripes, Macrodon, Gucullaa 

 (?), Pema; but probably those genera which contain minute 

 species only will yet be detected. 



Of the localities attached to the species in the following list, 

 " Putiki " means the upper sandy beds of the Wanganui system 

 in the neighbourhood of Wanganui. " Shakespeare Cliff" 

 means the blue clay at Shakespeare Cliff, and on the sea coast 

 near Wanganui. "Petane" means the district round Petane, 

 including Napier and Puketapu. 



Descriptions of the corals and Bryozoa from Wanganui will be 

 found in the " Palaeontology of New Zealand," part iv., by the 

 Eev. J. Tenison- Woods (Wellington, 1880). A few Bryozoa from 



