242 Notes on Post Tertiary Strata 



species have survived right down to the present day, we 

 may easily suppose that the eight forms which have now 

 become extinct were nevertheless living when the Limestone 

 Creek beds were deposited. 



The beds are, as yet, but partially examined, the only 

 collection of shells made being, I believe, my own, and at 

 each visit to the locality I have always succeeded in finding 

 new species. 



The actual proportion of living to extinct species is not^ 

 however, likely to be materially altered by further explora- 

 tions. This amounts, so far, to about 95 per cent., and the 

 deposit may therefore be fairly considered as of pleistocene 

 age. 



The height of the shell beds at Eoscoe's cannot be given 

 exactly, no levels having ever been taken in this part of the 

 country; but approximate aneroid measurements show that 

 they are from 75 to 100 feet above sea level. The bed of 

 the river here is probably not more than 40 feet above sea 

 level, though its waters have so far to travel before reaching 

 the ocean. The tide comes up the stream for about eighty 

 miles, and for this distance there is scarcely any fall. For 

 some miles from its mouth the bed is actually below sea 

 level, as proved by soundings. 



Between the river banks and the sea there is no low 

 ground whatever, the fall at the coast being very sudden. 

 The only possible theory, therefore, which can account for 

 this modern deposit is, that Roscoe's and the Limestone 

 Creek flats were in reality an old estuary of the Glenelg, 

 before the land to the south had risen. This estuary was 

 bounded on the east and west by high land, and sometimes 

 by cliffs of coralline limestone, ranging from 70 to 100 feet 

 above the level of the river at that time. Opposite Gilmore's 

 (between Roscoe's and Limestone Creek), a projecting tongue 

 of land extends for nearly a mile into the very centre of the 

 flatj which it divides into two parts for this distance. At 

 the top, it is only a few yards in width, and slopes rapidly 

 down to the terrace on either side, while it maintains 

 throughout the same general elevation as the table land 

 from which it springs, jutting out like a bold headland at 

 sea. Its sharp outline in the midst of this extensive and 

 almost level flat is very striking, and much more suggestive 

 of coast action than of that of a river current. On its sides, 

 the coralline limestone crops out, and the whole ridge con- 

 sists, no doubt, of harder portions of this rock, which the 



