158 T ransacfious. 



dark sandy shales, light-coloured and greenish-grey sands, sometimes glau- 

 conitic, in the upper part of which are very fragmentary fossil shells. The 

 dark sands weather brown, and occasionally have lenses of crystalline 

 calcite running through them. Farther down stream there is the same 

 alternation of sands and shales with lignite, and in one of the beds of sand, 

 about 2 chains above a fence crossing the creek, is a layer of shell-fragments 

 which include Struthiolaria tubercidata and Plejona kuttoni psei(dorarispina. 

 These beds pass down into the sands with numerous shell-fragments, to be 

 referred to later. 



The beds in the vicinity of the wool-scour strike north-west and dip 

 south-west at angles of about 20°, and they continue to do so for a little 

 distance up-stream, where lignite again occurs associated with greenish 

 sands, but above this the strike mugt swing sharply round till it becomes 

 east-north-east — that is, along the creek. As the beds are followed up- 

 stream, the dip becomes steeper, as much as 60'^, in agreement with the 

 strike and dip of the limestone, south of the road, forming the north-eastern 

 corner of Castle Hill. The beds here consist of greenish and yellowish white 

 sands and sandy shales, the latter occasionally carbonaceous. I was fortu- 

 nate on this occasion to be able to locate exactly the bed of Ostrea iiigens, 

 first recorded by Park,* for the heavy floods during the last season had 

 swept the face free from surface debris and exposed the fossil-bed clearly. 

 I had repeatedly searched for the bed without success, and am glad to give 

 confirmatory evidence of his interesting discovery. It was quite by over- 

 sight that I made no reference to this point in my original paper, and I 

 regret the omission. 



At the point where this bed is exposed the following series is shown on 

 the face of the clifi, the sequence being in ascending order and the total 

 thickness about 25ft.: (1) impure lignite; (2) sandy shales; (3) greyish 

 sands ; (4) sandy shales ; (5) greyish argillaceous sands ; (6) oyster-bed. 

 12 in. to 18 in. thick, in dark argillaceous matrix ; (7) greyish sandy shales ; 

 (8) greyish sands, weathering brown ; (9) white sands. 



Park is quite correct in his inference that this oyster-bed (6) is consider- 

 ably higher than the beds developed just above the limestone gorge of thi' 

 Porter, since this bed is probably at a higher level than that occurring 

 opposite the wool-scour, which is undoubtedly at a higher level strati- 

 graphically than that containing numerous Struthiolaria, which in turn over- 

 lies the limestone. However, the exact correlation of the two oyster-beds 

 is a matter of doubt owing to the absence of continuous exposure and the 

 slipped character of the country, especially the high banks of the Thomas, 

 where they are overlain by gravels. Although shell-fragments were observed 

 higher up the stream still, above the road-crossing, no other bed of oysters 

 was located, although it may easily occur buried up by surface debris The 

 occurrence of the Ostrea ingens indicates clearly that the beds associated 

 with it are of Mio -Pliocene age. 



Still another fossil horizon was located in the Porter River, about a mile 

 above the limestone gorge, and just below the junction of the river with a 

 rocky creek coming from Mount Torlesse. In the bed of the stream is a 

 small exposure of greensands containing numerous specimens of the black 

 oyster {Ostrea angasi). The beds strike north-east, and dip north-west 40°. 

 Associated with this is another bed containing fragmentary shells in poor 



* J. Park. .Mariae Tertiaries of Otago and Canterlniiv, Trans. S.Z. Inst., vol. 37, 

 p. 535, 1905. 



