the bed of this river, which is nearest to the Wollombi (or to Wambo
rather) I found an augitic rock, consisting of a mixture of felspar and
augite.

FOSSILS OF THE HUNTER.

Silicified fossil wood of a coniferous tree, is found abundantly in the
plains, and in rounded pebbles in the banks and bed of the river, also
chalcedony and compact brown haematite. A hill of some height on the
right bank, situate twenty-six miles from the seashore, is composed
chiefly of a volcanic grit of greenish grey colour, consisting
principally of felspar, and being in some parts slightly, in other parts
highly calcareous when the rock assumes a compact aspect. This deposit
contains numerous fossil shells, consisting chiefly of four distinct
species of a new genus, nearest to hippopodium; also a new species of
trochus; Atrypa glabra, and Spirifer, a shell occurring also in older
limestones of England.*

(*Footnote. These shells having been submitted to Mr. James De Carl
Sowerby, I am indebted to that gentleman for the following description:

Class Conchifera. Order, Dimyaria. Genus Megadesmus.

Valves equal, inequilateral, thick, their edges even; umbones nearly
central; hinge sunk, with an antiquated area and one ? or two ? large
teeth in each valve; ligament external, large; impressions of the
abducter muscles strong, nearly equal, united by the impression of the
mantle, at the posterior extremity of which is a small shallow sinus; no
lunette.