240 TKANSACTIOKS AND PKOCEEDINGS OF THE [Sess. lviii. 



line the sea becomes rapidly deeper, and at a distance of 

 only 8 miles from the coast of Mauritius the depth is 

 1350 fathoms, and at 20 miles 1870 fathoms, or 11,220 

 feet. It will, therefore, be observed that the islands of 

 the Mauritius group form the summit of a huge volcanic 

 mountain, the greater part of which is submerged beneath 

 the waters of the Indian Ocean. Eound Island, though 

 only 13 miles distant from Mauritius, and separated from 

 it by a shallow sea nowhere exceeding 43 fathoms, con- 

 tains several species of endemic plants and animals, which 

 are not found on ]\Iauritius itself. If these two islands 

 were ever connected together by dry land, it must have 

 been at a very remote period, before such differences could 

 have occurred in their floras and faunas. How much 

 more remote then must have been the time when such 

 islands as Mauritius, Bourbon, and Eodriguez were 

 supposed to have formed part of an ancient continent, 

 when these islands are now separated by an ocean over 

 11,000 feet deep. The floras and faunas of the Mascaren 

 Islands are of the same type, and the different islands, 

 besides containing their own peculiar endemic species, 

 also contain species common to the other islands of the 

 group, as well as several species widely distributed over 

 other parts of the world. 



Round Island is not surrounded by a coral reef ; and 

 in consequence of its exposed position to the surf, caused 

 by the prevailing south-east trade wind, it is only possible 

 to land on the island after a spell of calm weather. Even 

 then a landing is only possible at two points, one on the 

 west and the other on the south-west side of the island. 



Lieutenant-Colonel J. A. Lloyd, Surveyor-General of 

 Mauritius, visited Round Island on 16th December 1844, 

 and was storm-stayed for seven days. His attention 

 was chiefly directed to the geology of the island ; and 

 an account of his visit is published in the " Transactions 

 of the Natural History Society of Mauritius " for the years 

 1842-45, pp. 154-161. He also visited Serpent Island ,^ 

 the most remote of the Mauritius group. Colonel Lloyd 

 only refers to the flora and fauna in a general wa}', and 

 the paper published by him deals chiefly with the geology 

 of the island. 



