river-gravel takes its place. "The grits, sands and clays forming the proper coal measures are here overlaid by limonitic sandstones and a gritty calcareous rock full of shell fragments that almost without exception belong to a species of oyster that cannot be distinguished from the black oyster of the Malvern Hills, Canterbury. In the same beds occur numerous fusiform bodies, respecting the zoological affinities of which there has long been a difference of opinion, viz., whether they should be referred to the belemnitidæ or simply considered cidaris spines changed to aragonite, and thus acquiring a fibrous, radiated structure. Fortunately, among a considerable series of these fossils collected by Mr McKay on this occasion, there prove to be at least two specimens showing distinct traces of an alveolar cavity (no phragmacone being present); and there is also another specimen preserving the upper portion of the guard sufficiently well to show that originally there was a ventral groove or fissure, the lower part of which can be traced in the shell structure. This would indicate that the fossil is a species of belemnitella, and not a true belemnite." (Geological Survey report 1886–87, p. xxix.) As the actual determination of this organism is obviously a matter of great importance in determining the age of the coals, it has been thought better to quote Sir James Hector's remarks in full.
Above the locality here referred to, to the south-west, the hill rises to a height of 1560 feet, and is capped by the dolerites and basalts of Saddle Hill. Round the edges of the schists, the coal-measures follow the former land area, to an out-crop at the Halfway Bush, but the coal there has the character of a bituminous shale, and contains a large proportion of ash. In the Water of Leith, fragments of coal have been found, which indicate that the seams in that direction have been altered by the igneous rocks; one specimen, stated to have been found in the Botanic Garden Reserve, had the property of caking, which is quite exceptional, even among the altered brown coals.
It is now necessary to return to the point where we left the schists, and resume our course over the coal-measures, noting how the working of the seams at Green Island has caused numerous fractures of the surface. Shortly before arriving at
