394 Transactions. — Geology. 



southern Otago, the cementing medium of the grits is brown 

 peroxide of iron, and here also these beds possess their 

 usual flaggy structure. Where the iron-peroxide occurs in 

 large excess it presents a fine mammillary structure in- 

 crusted on the flat surface of the grit-stone. 



These quartz grits, generally known as coal grits from 

 their close association with the brown coals of Otago, in 

 most places contain traces of gold originally derived from the 

 schists from which they were formed. And, although the 

 grits themselves have seldom or never been found sufficiently 

 rich to be worked directly for their gold contents, it is, never- 

 theless, of importance to mention that much of the alluvial 

 gold of Otago has been derived from a rewash of the grits 

 in which the gold has been collected in a more concentrated 

 form. 



The area occupied by the grits is much obscured by 

 surface earths and masses of basalt, which render it im- 

 possible to measure the thickness of these beds, or ever 

 determine whether the fireclays and brown coal which usually 

 accompany them are present here or not. 



(c.) Glauconitic Sandstone. — This rock is well exposed at 

 the phosphate-quarry workings at Kiln Point, opposite 

 Clarendon, and at Millburn quarry. The section at the 

 former place is obscured with slope deposits, and in conse- 

 quence the thickness of the sandstone could not be deter- 

 mined accurately, but it is probably not less than 40 ft. or 

 50 ft. At Millburn a thickness of 40 ft. is visible below the 

 limestone, and there also the base of the section is not seen. 



The sandstone is generally coarse in texture, and, except 

 where it is highly calcareous, never shows any planes of 

 stratification. It contains a considerable proportion of glau- 

 conite, the hydrous silicate of iron and alumina to which the 

 rock owes its greenish colour. 



At Kiln Point this sandstone was found to contain a few 

 species of marine Mollusca, mostly broken and fragmentary. 

 Of these were collected a large smooth Pecten, probably 

 Pecten hochstetteri ; a small Pecten with large distinct ribs, 

 probably P. loilliamsoni ; and Serjnda. In addition to these 

 Mr. R. Ewing found a very large shark's tooth. 



At Millburn quarry were found Pecten hochstetteri, a frag- 

 ment of a large strongly ribbed Pecten or Lima, Seryula 

 (two species), Balanus, and a species of small oyster. And 

 at the Millburn Company's phosphate-workings, which are 

 situated about a quarter of a mile east of the quarry, from the 

 greensand where oxidized to a rusty-brown colour were col- 

 lected a Turbo, Voluta, Leda, Tapes, Venus, Waldheimia, 

 Dcntalium, Flabellum, and fish-teeth. 



These forms are all characteristic of shallow-water con- 





