MESOZOIC PLAIXS OF SOUTH AUSTRALIA. 243 



and pebbles, as in the Stony Desert of the Diamentina, in 

 others the jasper rock lies scattered in slag-like masses and lumps, 

 on tlie soft loamy surface of the plains, together with gravel 

 shingle, and fragments of agate, chalcedony, quartz, flint, &o. Tt 

 is difficult to account for the even distribution of these gravel, 

 and rock fragments over such a large extent of plain surfaces, 

 floating ice being the only agent likely to produce such results. 

 Below and surrounding the table-hills and stony downs, are the 

 soft silt plains, which, together with the former, cover the gypseous 

 clays, marls, calcareous shales, limestone, sand, and gravel drifts 

 of Cretaceous age. The greatest thickness of these beds, which 

 has been proved by boi'ing at Tarkininna, is about 1,200 feet. 

 The mound springs, which are the natural indicators of artesian 

 water beneath these plains, are found in many places near 

 the outcrops of bed rock, between the junction of which 

 and the Cretaceous rocks the water has, doubtless, found an 

 easier egress. On the surface, the water often forms accumula- 

 tions of travertine limestone rising to heights of forty or flfty 

 feet, and showing in the distance across the level plains, where 

 there is a group of springs, like a low range of hills ; the deposition 

 of this limestone has in many instances formed raised cups or 

 basins, over the edges of which the water flows. The water of 

 these springs contains soda, and is genei'ally good drinking water ; 

 in some cases, however, in the same group of springs, there is a 

 great diflerence in the quality of the water, which in one spring 

 may be di'inkable, and in another, a few feet away, salt. As a 

 rule these spring waters are warm, and must have a considerable 

 temperature beneath the surface. Bores have been sunk by the 

 Government in this formation at Tarkininna, where artesian water 

 was tapped at 1,200 feet, and at Hergott, Coward Springs, 

 Strangway Spi'ings, &c., where a large supply of water was attained 

 at an average depth of some three hundred feet. The supply from 

 some of these bores is over 1,000,000 gallons per day. The supply 

 is doubtless partly derived from a vast wide spread ai^ea of under- 

 ground drifts which are fed from the ranges at the heads of the 

 Cooper, Diamentina, and other rivers, although it appears most 

 likely that there are other sources of supply in the form of deep- 

 seated hot springs beneath the deep Mesozoic basin. The fossils 

 Avhich occur in this formation are found in masses and nodules of 

 limestones, and in the calcareous shales, but generally they are most 

 plentiful in the former, which are often entirely composed of them. 

 A collection lately made by me, in the Lake Eyre district, was 

 sent to Dr. H Woodward, of the British Museum, for exami- 

 nation, including an Ammonite about two inches in diameter, from 

 Primrose Springs. A portion of the same collection has been 

 examined and named by Professor Tate, and is now in the 

 Melbourne Centennial Exhibition. Other fossils I had previously 

 forwarded to Dr. Woodward from the same district, were 



