294 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



but the numbers and distinctions of the species were involved 

 in considerable doubt. With a view to settle the doubtful 

 questions, Dr. Giinther, of the British Museum, availed him- 

 self of the chance afforded him by considerable collections 

 amassed from time to time in London, and chiefly at the 

 British Museum, and has investigated the species and their 

 distinctions. In a recently published richly illustrated vol- 

 ume he has given the results of his final examinations. Not 

 less than fifteen species have been recognized either in a 

 living condition or recently exterminated ; these can be seg- 

 regated into several groups coincident with their geograph- 

 ical ransfe and distinguished by characters derived from the 

 shell, so that hitherto indeterminable shells in museums may 

 be at least referred almost certainly to the archipelago from 

 which they may have been derived, even if no other informa- 

 tion can be obtained. The tortoises of the Aldabra Islands 

 have a small anterior unpaired "nuchal" plate in the upper 

 shell, or carapace, and a pair of anterior gular plates in the 

 lower or plastron ; those of the Mascarenes have no nuchal, 

 and the gular is single ; and those of the Galapagos are also 

 destitute of the nuchal plate, but have a pair of gular ones. 

 So localized are the species that each island almost has its 

 own peculiar form. On the Aldabra Islands still survive at 

 least three, if not four species, and from the Galapagos Islands 

 five living and one extinct species have been obtained ; but all 

 of the Mascarene species (five are known from their remains) 

 have become extinct, and since their discovery by the Euro- 

 peans. The several groups of islands inhabited by these tor- 

 toises, as will be recognized, are quite widely distant, and, in 

 the case of the Galapagos, on the one hand, and the remaining 

 islands, on the other, almost as widely separate as could be. 

 They are all situated in the intertropical zone, but have in 

 common otherwise only the negative characteristic of the 

 absence of large terrestrial mammals and that of human in- 

 habitants until recent times. These are doubtless the con- 

 ditions which favored their development and increase. His- 

 torical evidence shows that species existed on all the islands, 

 and were very abundant in individuals. They were exter- 

 minated in the Mascarene Islands after their settlement, and 

 but for the absence of permanent settlements on the others 

 would probably have entirely disappeared from the existing 



