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Show 164 LARVJS OP INSECTS- SINGULAR FORMATIONS. of rocks projecting from the mud- plain which surrounds the island. In wading to the shore, we struggled through a deep, soft, dark-coloured mass of what at first appeared to be ooze and slimy mud, but which, upon examination, proved to consist almost solely of the larvae of insects lying upon the bottom, producing, when disturbed, a most offensive and nauseous odour. The mass was more than a foot in thickness add extended several yards from the shore. A belt of soft, black mud, more than knee- deep, lay between the water and the hard, rocky beach, and seemed to be impregnated with all the villanous smells which nature's laboratory was capable of producing. The point where we had effected our landing was found to be a protrusion of an isolated pile of metamorphic rock above the vast mud- plain, which latter extended to the northward and eastward, without a shrub or a bush or a blade of grass to be seen upon its surface. This protrusion consisted of various kinds of rock, pushed up from beneath, with a dip to the west from nearly perpendicular to 45°. Slate, almost vertical, was found lying side by side with a dark rock filled with pebbles and stones as large as a man's head, consisting of what appeared to me to be granite altered and burned by intense heat. This dark rock presented some indis-* tinct traces of a lammated structure, and may be slate very much fused. Large boulders of granite and feldspar or quartz, with scales of mica, lay strewn about, and I observed one with several well- defined cubes of iron pyrites imbedded in it. The slate seemed to be completely filled with pebbles and small broken fragments of granite rock, with here and there a cube of iron pyrites. Boulders of feldspathic rock, seamed with white quartz, and containing thin veins of jasper of a brick- red colour, are occasionally found in the slate. Near the western extremity of the point is a different kind of rock- the direction nearly perpendicular. It is of a more sandy structure, but is filled with the same pebbles. The whole has been in a state of fusion. The mud- flat, where above the level of the water, is thickly covered with round, dark- coloured, circular cakes, precisely resembling, in form, colour, and appearance, the excrement of cattle dried in the sun. Underneath the dry surface of these cakes is a soft, black, and sometimes greenish mud, which, when the cake is moved by the foot, and the dry covering pushed aside, emits a most fetid, sulphurous odour, poisoning all the surrounding air. The substance of which these lumps are formed appears to have |