A little below this singular place, the country again declines, when a tertiary fossil formation shows itself, which, rising gradually as an inclined plain, ultimately attains an elevation of 300 feet. This formation continues to the very coast, since large ma.s.ses of the rock were observed in the channel of communication between the lake and the ocean; and the hills to the left of the channel were based upon it. This great bank cannot, therefore, average less than from seventy to ninety miles in width. At its commencement, it strikingly resembled skulls piled one on the other, as well in colour as appearance. This effect had been produced by the constant rippling of water against the rock. The softer parts had been washed away, and the sh.e.l.ls (a bed of Turritella) alone remained.
Plate 1, Figures 1, 2, and 3, represent the selenite formation.
Plate 2, represents a ma.s.s of the rock containing numerous kinds of sh.e.l.ls, of which the following are the most conspicuous:
Cardium Pectunculus Corbula Arca Conus, and Others unknown.
The following is a list of the fossils collected from various parts of this formation, from which it is evident that a closer examination would lead to the discovery of numberless species.
TUNICATA.
PLATE III.
FIG.1 Eschara celleporacea.
2 ------- piriformis.
3 ------- UNNAMED.
FIG.4 Cellepora echinata.
5 --------- escharoides?
6 Retepora disticha.
7 -------- vibicata.
8 Glauconome rhombifera.
All Tertiary in Westphalia and England.
RADIATA
9 Scutella.
10 Spatangus Hoffmanni--Goldfuss.
Tertiary, in Westphalia.
11 Echinus.
CONCHIFERA--BIVALVED Sh.e.l.lS.
Corbula gallica--Paris basin--Tertiary.
Tellina?
Corbis lamellosa--Tertiary--Paris.
Lucina.
Venus (Cytherea) laevigata--ibid.
----- ---------- obliqua --ibid.
Venus Cardium?--fragments.
12 Nucula--such is found in London clay.
13 Pecten coarctatus?--Placentia.
------ various?--recent.
14 ------ species unknown.
Two other Pectens also occur.
Ostrea elongata--Deshayes.
15 Terebratula.
16 One cast, genus unknown, perhaps a Cardium.
MOLUSCA--UNIVALVED Sh.e.l.lS.
Bulla? Plate II., fig. 2.
FIG.17 Natica--small.
18 ------ large species.
Dentalium?
19 Trochus.
20 Turritella.
---------- in gyps.
21 Murex.
22 Buccinum?
23 Mitra.
24 ----- very short.
25 Cypraea.
26 Conus.
27 ----- (Plate II., fig. 3.) 28 Two, unknown, (Also Plate II, fig. 4.) The above all appear to belong to the newer tertiary formations.
[Fig.17 to 27--These genera are scarcely ever, and some of them not at all, found in any but tertiary formations.]
A block of coa.r.s.e red granite forms an island in the centre of the river near the lake, but is nowhere else visible, although it is very probably the basis of the surrounding country.
ROCK FORMATION OF THE COAST RANGE OF ST. VINCENT"S GULF.
Primitive Transition Limestone.--Light grey, striped. Altered in appearance by volcanic action; occurs on the Ranges north of Cape Jervis.
Granite.--Colour, red; found on the west side of Encounter Bay.
Brown Spar.--South point of Cape Jervis.
Sandstone, Old Red.--East coast of St, Vincent"s Gulf.
Limestone, Transition.--Colour, blue. East Coast of St. Vincent"s Gulf.
Formation near the first inlet. Continuing to the base of the Ranges.
Clay Slate.--Composition of the lower part of the Mount Lofty Range.