DESCRIPTION OF THE EXPEDITION, 161 
granitic masses which lie scattered in the seas of the vicinity, and such reefs or flats as 
occur round the islands. A glance at the chart shows that these latter exist here and 
there around all the granite-formed islands of the Seychelles, especially in bays. In 
ordinary language it would be said that they generally possess scattered /ringing-reefs. 
Where of any size, as off Céte d’Or and St. Anne’s Bay, both Praslin, and off La Digue, 
parts which we especially examined, these reefs are, so to speak, supported by islets or 
masses of granite in their edges or extending out within them for some distance from 
the land; the same statement is also true of the reefs off the northern half of Mahé. 
Their surfaces are covered over with several species of Cymodocea and large green alge. 
At their seaward edges corals grow, but they are generally rather isolated and of 
relatively small size. Lithothamnia practically do not enter into their composition, and 
hence the well-consolidated and distinct edge, characteristic of what are usually termed 
coral-reefs, is absent. Most have actually owed their origin to the piling up of 
caleareous and siliceous sand in bays, or to the cutting down and removal of the 
granite above the sea-level. They are not fringing-reefs in the ordinary acceptance of 
the term, such as we found round most parts of Mauritius and such as commonly oceur 
in tropical waters fringing continents or isolated volcanic and other islands, the slopes of 
which tail off rapidly to some hundreds of fathoms. Praslin, Mahé, and the other 
granitic islands of the Seychelles are mere peaks on the centre of a large bank, and their 
flats at the low-tide level should rather be compared to the shore-flats round islets 
within barrier-reefs, such as are frequently found in Fiji and other groups. In situation 
they are similar to shoals within the lagoons of the Chagos Atolls, and to shoals and the 
shore-reefs round islets within Maldivan lagoons *. These, however, have a different 
origin, and the reefs round Mahé, &c., have no real homologues in the Indian Ocean, 
Caution will hence have to be exercised in making any deductions from the presence on 
or absence from them of any species or genera of animals or plants as compared to 
other reefs +. 
After our return to Mahé we visited North and Silhouette Islands. Cooper remained 
on the latter for three weeks, occupying a house on the shore, placed at his disposal by 
Mr. Chas. Dauban, who owns the island. He devoted himself particularly to an 
examination of its physical and geological features, also searching unsuccessfully for 
traces of the crocodiles stated to be formerly common on its shores. In five places 
around its coast he found masses of coral attached to the granite at various heights up 
to 30 feet above the sea, proving a recent elevation of the island of at least that amount. 
Gardiner meantime explored Mahé, finding traces of a similar elevation as well as of an 
earlier one of upwards of 200 feet. 
We collected in both Silhouette and Mahé, but conditions were much more favourable 
in the latter, as there were better tracks up to the jungles of Morne Seychellois 
* Vide pp. 158-171 of ‘Fauna and Geogr. Maldives and Laccadives.’ Also “The Coral Reefs of Funafuti, &c.,” 
Proc. Camb. Phil. Soc. vol. ix. pp. 438-443 for a typical fringing-reef, and pp. 464-6 for a barrier-reef with 
shore-flats round an island. 
+ Before leaving Praslin we must express our obligations to Dr. Laidlaw and Mr. Tregarthen for assistauce on 
that island. 
23* 
