49
by a large tertiary formation, containing beds of limestone, full of fossil shells of existing genera. From this point to the banks of the river Murray, we have no published accounts of the country, but I have always heard it spoken of as low, nearly flat, and consisting generally of barren plains. A little west of the Glenelg are the "biscuit plains," so called because they are covered with thickish, flat, round stones, of the shape and appearance of a sea-biscuit. These are generally smooth above, and have a curious cellular structure below, but whether they are the remains of anything organic, or merely concretions or incrustations, I have not been able to ascertain. On arriving at the banks of the Murray below the junction of the Darling, and thence to Lake Alexandrina, we find the tertiary formation alone exposed. Captain Sturt describes this formation both in his first travels and in those lately published, figuring many of the fossils in the Appendix to the first.
In his last publication, "Sturt's Expedition into Central Australia," he describes the "fossil formation," as he calls it, as rising to the west on the bank of the Murray near Lake Bonny (long. 140° 30') to a height of 250 feet, as having thence a regularly horizontal stratification, with a gently undulating surface round the great bend of the Murray, till on approaching Lake Alexandrina, it suddenly dips and disappears. He says, "its lower part is entirely composed of turritellæ, but every
