Norman Taylor — The Cudgegong Diamond Field. 399 



As may be partly seen from the section (which shows its northern 

 side only), the freshwater remains occupy the site of an old hollow, 

 which is not even yet quite filled up. This hollow existed even in the 

 " Basement " clay ; is continued in the " Purple " clay, and also in the 

 glacial gravels which overlie the Boulder-clay, and which are so 

 strangely, apparently, thrust into it (B. of section) ; and finally it 

 has been, in recent times, the bed of a pond, which has thrown 

 down the thick bed of marl (A.), partially obliterating the hollow. 



This recent marl offers a strongly marked contrast to the ancient 

 bed in the variety of its shells, which are of many species, of Cyclas, 

 Planorbis, Limncea, Bithynia, etc. ; whilst the old bed, though so rich 

 in individuals, can count but one species ; as though, by some 

 chance, this one shell had, by virtue of its habits, gained a footing, 

 and had increased, undisturbed by any competitors, which at a 

 later period found the same position so favourable to them. I have 

 not seen Limncea peregra in the recent marl. 



In conclusion, I may mention the similarity between these fresh- 

 water fragments and the so-called " Bridlington Crag," with regard 

 to their relations to the respective Boulder-clays which accompany 

 them. In an exposure of the " Basement " clay, on the beach 

 opposite the terraces which protect the town, which was bared in 

 March last, I saw several separate streaks of a fine, clean, blue clay, 

 and also of a sandy clay, twisted and distorted amidst the Boulder- 

 clay. These streaks contained marine shells of the well-known 

 Bridlington species — Astarte borealis, Tellina balthica, Cardita 

 borealis, Natica clausa, etc. Some of these shells were perfect, but 

 more were crushed as they lay, and the fragments more or less 

 separated, as if by the shearing under pressure of their yielding 

 clayey matrix. In a precisely similar manner were the freshwater 

 clays drawn out in their Boulder-clay, with the shells similarly 

 scattered, though not generally so broken. 



Thus the movement of the ice at one time over a soft sea-bottom, 

 and, at another, over the silty bed of a pond, has produced precisely 

 similar effects. And the same ice, which cut up the freshwater 

 deposits in this manner, has passed over the sand and laminated 

 clay not 100 yards to the north, and has left scarcely a sign of its 

 passage. 



III. — On the Cudgegong Diamond Field, New South Wales. 



By Norman Taylor, Esq., of the late Geological Survey of Victoria. 



Communicated by K. Etheridge, jun., F.G.S. ; of the British Museum. 



SINCE the publication, in the Quarterly Journal of Science for 

 July, 1876, of an article on the Indian Diamond Fields, in 

 which the writer, Captain Burton, does not appear to be aware of 

 what has been done in these Colonies towards adding to our know- 

 ledge of the geological history of the diamond, I have been induced 

 to re-write a paper, jointly prepared by the late Professor Alex. M. 

 Thomson, of the Sydney University, and myself, and read before 



