HuTTON. — Oeology of the Waihao Valley. 431 



The right bank of the Waihao Eiver, from a little above the 

 Forks down to the bridge by which the road from Aruo to Wai- 

 kakahi crosses the river — a distance of about three miles — is 

 formed hy rocks of the Oamaru System. A northerly extension 

 of these rocks, rather more than a mile in breadth, crosses the 

 river about half a mile below the Forks ; so that, for this dis- 

 tance, the Oamaru System"- forms both banks of the river. On 

 these points all are in agreement. The rocks belonging to the 

 Oamaru System here are — 



3. Pale-yellow arenaceous limestone, about 50 feet thick, 



known as the Waihao limestone. 

 2. Calcareous sandstone, with green grains, 150 feet. 

 1. Dark-grey marl, getting more sandy at the top, with 



ferruginous bauds or veins ; thickness, 50 feet + ; 



contains Fecten zittelli. 



No rock is seen to underlie this marl anywhere between the 

 forks of the Waihao and its mouth. 



On the left bank of the river, both above and below this 

 northerly extension of the Oamaru System, we find thick (200 

 feet + ) beds of soft dark-green or grey argillaceous sandstone, 

 sometimes with calcareous concretions, and containing numerous 

 fossils {sec fig.) It was from these beds that Dr. von Haast 

 collected the fossils sent me in 1875. They are also the " marly- 

 greensands" of Mr. McKay's report. The point to be settled is : 

 Do these greensands underlie the marl of the Oamaru System ? 

 or do they lie unconformably against the eroded edges of that 

 system ? 



The palgeontological evidence is decidedly in favour of the 

 second of these suppositions, as the following list of fossils from 

 the Waihao Forks will show : — 



1. Teeth of crocodile (?). 



2. Aturia ziczac, Sowb. 



'■'3. Siphonalia nodosa, Martyn. 



^'4:. Ancillaria australis, Sowb. 



5. Ancillaria hebera, Hutton. 



*6. Voluta corrugata, Hutton. 



*7. Pleurotoma fusiformis, Hutton. 



"•'8. Pleurotoma huchanani, Hutton. 



"^'9. Pleurotoma aivamoaensis, Hutton. 



*10. Clathurella hamiltoni, Hutton. 



11. Natica gihhosa, Hutton. 



12. Natica hamiltoni, Tate. 

 *13. Natica suturalis, Hutton. 



14. Dentalium mantelli, Zittel. 



* For a list of fossils found in these rocks, and a discussion as to their 

 age, see "Quar. Jour. Geol. Soc. of London," vol. xli., p. 559. 



