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Porcellana, Atergitns, Scilla, Alpheus, etc., and a large variety oi
Corals and Polyzoa.
One of the most conspicuous objects about the foreshore at
Port Mahe is a curious fish of the genus Periophthalmus, which
may be seen not only jumping about the dry mud flats at low
water, but also climbing up the rugged vertical faces of the blocks
of granite of which the sea-wall and pier are formed. It is very
difficult indeed to catch one, as I have good reason to know.
Associated with them were several species of crabs, among which
I recognized representatives of the genera Macrophthalmus, Gela-
simus, Grapsus, and Ocypoda.
The Seychelles are peculiar in being the only small tropical
oceanic islands of granitic structure. All the others, excepting
St. Paul’s Rocks, are either of volcanic or coral formation. The
rock about Port Mahe is a syenitic granite, in which the mica of
ordinary granite is replaced by hornblende. In some cases the
felspar is coloured blue, in others reddish, and in every instance
it occurred in large coarse crystals. The soilcap was a reddish
pasty clay, of great thickness. In one of the road cuttings near
the settlement a section of this clay fully ten feet in depth was
exposed.
We left Mahe on the 14th of March, and on the following day
anchored off a small coral islet, the northernmost of the Amirante
Group. This, with another similar islet adjoining, constitute the
African Islands. A party of surveyors immediately landed in
order to fix on a suitable place for taking midnight observations
of the stars, and I had soon afterwards an opportunity of landing
to explore. The islet is two hundred yards long, by about sixty
yards in width, is more or less elliptical in outline, low, and flat,
and for about three-fourths of its circumference is girt by a
smooth beach of coral sand, on the surface of which I noticed
a prodigious number of Orbitolites discs. The northern end of
the islet is composed of upraised coral sandstone, which has been
grooved and honeycombed into various fantastic shapes, so that