GIANT TORTOISES AND THEIR DISTRIBUTION 309 



a peculiarity seems very unlikely to have been acquired in- 

 dependently in two widely sundered groups of islands ; if 

 indicative of community of descent, it is of great importance 

 in regard to the mutual relationship of the species from the 

 two oceans. 



Turning to the tortoises of the Galapagos group, it may be 

 premised that these have not suffered (or at all events had not 

 done so a few years ago) to anything like the same extent from 

 foraging expeditions by the crews of vessels as their relatives 

 of the islands of the Indian Ocean. Nevertheless, some of the 

 islands, such as Charles, Duncan and Chatham, have been 

 denuded of their tortoises ; although, after much trouble and 

 no inconsiderable amount of more or less unavoidable error, 

 it has been found possible to identify the species by which 

 they were respectively inhabited. James Island, for instance, is 

 known to have been the home of tortoises of a broad and 

 flattened type, as distinct from the members of the saddle- 

 backed group ; it is therefore probable that it was inhabited 

 by T. nigrita, while the allied T. nigra (= elcpliantopiis) and 

 T. vicitia were natives of South Albemarle, and T. microphyes 

 represented this group in North Albemarle. In one of his 

 later papers Mr. Rothschild has described, under the name 

 of T. zvallacei, a large shell formerly in Bullock's Museum, 

 Piccadilly, which there is every reason to believe came from 

 Chatham Island. Of the so-called saddle-backed group, dis- 

 tinguished by the pinched-in form and extreme tenuity of the 

 shell, which is scarcely thicker than paper, four specific repre- 

 sentatives are known, namely, T. ephippium of Duncan Island, 

 T. becki from North Albemarle, T. abingdoni from Abingdon 

 and T. galapagoensis from Charles Island, the last-named being 

 the one referred to above as exhibiting a type of cervical 

 vertebrae found elsewhere only in the Aldabra tortoises. 



As a group, the Galapagos tortoises are distinguished by 

 their long necks and limbs, the flattened head, the absence of 

 a nuchal shield on the upper, and the paired gular shields 

 on the lower shell. Except for the last-named feature, these 

 tortoises are indeed very closely related to those of the Mas- 

 carene Islands, and therefore widely different from the round- 

 headed Aldabra species ; they are also distinguished, although 

 in a somewhat less degree, from the double-gulared Seychelles 

 species. 



