June 29th.
Left Fitzroy Island for an anchorage under Cape Grafton, where we remained for the three following days. While running down to the anchorage we entered a large patch of discoloured water, with a perfectly defined margin, yet the lead showed no difference in the depth or nature of the bottom. It would also appear that since Captain King's survey the water has been shoaling hereabouts. On a small island inshore, the skull of a crocodile was found upon the beach, and this reminds me that several of these animals were seen in one of the rivers of Rockingham Bay. The Australian alligator, as it is usually called, is a true crocodile, identical, according to Mr. Gray, with the common Indian species.
ISLET IN TRINITY BAY.
July 3rd.
Ran to the north-west fifteen miles, and, after having anchored midway to form a surveying station, brought up finally under a small unnamed islet in Trinity Bay. This island, viewed from our anchorage on its north-west side, presents the appearance of a ridge connecting two rounded eminences, with a sharp sea-face exposing the stratification of the rock. This is a micaceous rock, assuming at one place the appearance of mica slate, and at another being a conglomerate, with frequent veins of quartz. The strata, which are often flexuous, or slightly contorted, have a westerly dip of 60 degrees, and the strike is North-North-West and South-South-East. On the windward side there is a long gradual slope, covered with tall coarse grass, among which many quail were found. The shore is fringed with the usual maritime trees and bushes, and an extensive mangrove bed runs out upon the reef in one place. This reef is of great extent, stretching out to windward upwards of a mile, as far as a small rocky isle like a haycock.
LOW ISLES.
On July 7th we anchored to leeward of the Low Isles, in the northern part of Trinity Bay, in eight fathoms, mud, half a mile from the shore, and remained there for the four succeeding days. This small group may be said to consist of three islets. One is low, sandy, and well wooded, about 300 yards in diameter, and is situated at the north-west extremity of a horse-shoe reef, with its concavity to leeward; the other two may be looked upon as merely groves of mangroves on the reef, the roots of which are washed at high-water, except in a few places, where narrow ridges of dead coral have afforded footing for the growth of a samphire-looking plant (Salicornia indica). The sandy islet presents no remarkable feature. The remains of burnt turtle bones indicate the occasional visits of natives from the mainland. A solitary megapodius was shot, but the only other land-birds are a little yellow Zosterops, and the larger ground-dove (Geopelia humeralis).
ANIMALS OF A CORAL REEF.
During our stay we were fortunate in having fine weather, light winds, and low tides, which enabled such as were inclined to look for shells upon the reef to do so under the most favourable circumstances. This reef is of great extent, with all the varieties of coral, mud, and sand, and proved a most productive one. A sketch of the distribution of the principal of its productions may be of interest to some. Many kinds of fishes, Muraena, Diodon, Balistes, Serranus, etc. are found in the pools among the coral blocks; the first of these, of bright colours variously striped and spotted, resemble water-snakes, and are exceedingly active, gliding through the interstices in the coral and hiding in its hollows--they bite savagely at a stick presented to them, and are by no means pleasant neighbours while wading about knee-deep and with bare arms turning over the coral which they frequent. On a former occasion I had been laid hold of by the thumb, and the wound was a long time in healing. Crustacea are also numerous; blue and green Gonodactyli leap about with a sharp clicking noise--legions of Mycteris subverrucata traverse the dry sands at low-water--and in the shallow muddy pools, dull green Thalamitae and Lupeae swim off rapidly, and smooth Calappae seek refuge by burrowing under the surface.
Of mollusca, two species of olive (O. Erythrostoma and O. leucophoea) were found on the sandy margin of the islet--several Cerithia and Subulae (S. maculata and S. oculata) creep along the sand flats, and, with some fine Naticae, and a Pyramidella, may be found by tracing the marks of their long burrows. Several Strombi and Nassa coronata inhabit the shallow sandy pools; the egg-shell and many Cypraeae occur under coral blocks, which, when over sand, often harbour different kinds of cones--of which the handsome C. textile is the commonest. A delicate white Lima (Lima fragilis) is abundant here, merrily swimming away in the pool under an upturned stone, and leaving its fringe-like tentacles adhering to the hand when seized. Lastly, it would be improper to omit mentioning the very fine oysters adhering to the roots of the mangroves. But these are only a small portion of the shellfish collected here. Among radiate animals, several Ophiurae and Ophiocomae and other Asteriadae, with two kinds of Echinus, are also plentiful under blocks of coral (Astraea and Maeandrina) in the pools; one of the last, remarkable for its very long, slender, black spines, has the power of giving an exceedingly painful puncture, if carelessly handled--for a few minutes the sensation is similar to that caused by the sting of a wasp; of the others, a fine Ophiura is remarkable for its great size and grass-green colour, and an Ophiocoma for the prodigious length of its arms.