102 Dorothea Bate — A Gigantic Land Tortoise 



of the Galapagos Islands, notably in T. alingdonii, which " has 

 a carapace almost as thin as paper in most parts ".' On the other hand, 

 other isolated forms have thick shells, so it seems that some other 

 explanation is required to account for the variation in this respect. 

 Dr. Giinther^ may have been near the truth when he reiuarked that 

 this character probably was influenced by the nature of their food and 

 was correlated with their mode of progression. The very great 

 and consistent difference in the size of horns carried by a single 

 species, especially among the deer, in different parts of its habitat 

 is well known, and may perhaps be analogous to the varying thickness 

 of shell in the giant tortoises. 



It seems necessary to suppose that there have been considerable 

 changes of climate and vegetation since these giant tortoises roamed 

 the island. That Menorca already was an island is indicated by the 

 discovery of remains of a large race of lerot, probably an insular form. 

 At the present day a small species of land tortoise, T. gr^ca, is found 

 in Menorca. 



It will be seen from the following description of the Menorcan 

 giant tortoise remains that these neither present any very salient 

 points for the differentiation of the species nor indications as to with 

 which form they are most closely related. Therefore it seems 

 advisable to bestow a distinguishing name, at least pi'ovisionally 

 on this race, wliich I therefore propose should be known as 

 T. gymnesicus, sp. nov. 



It is thought that a brief description of the chief specimens 

 obtained may be of use and interest. 



Desceiption' of Specimens. 



Unfortunately no portion of the skull was recovered and only 

 a single cervical vertebra of moderate size and in a very bad state 

 of preservation. 



Carapace. — This is represented by tliree fragments; one of these 

 is evidently part of a left anterior marginal plate and in shape 

 resembles those of the Madagascan T. grandidieri, sloping gently 

 down and having a rounded edge, in marked contrast to some of 

 the earlier Egyptian forms with sharp-edged and abruptly recurved 

 marginal plates. The Menorcan example, which is 17 cm. in length, 

 is slightly convex in outline, and at one end retains part of the line 

 of junction with the next plate. It attains a thickness of 33-5 mm., 

 thus surpassing by some 13 mm. any among a number of fragments 

 from the Maltese caves. ^ 



A second Menorcan specimen, still partially embedded in the hard 

 red matrix, is convex in outline and attains a thickness of 27 mm. 

 It is probably part of one of the neural plates, and indicates that 

 there was no great difference in the thickness of the various portions 

 of the carapace, such as obtains in that of some species in which the 

 dorsal area is very much thinner than the periphery. 



A third fragment of plate is only 18 mm. thick. 



^ Eothschild, Novitates Zoologicm, vol. iii, p. 85, 1896. 



^ Gigantic Land Tortoises, London, p. 24, note, 1877. 



^ Leith Adams, Quart. Journ. Geol. Soc, vol. xxxiii, p. 178, 1877. 



