froin the Pleistocene of Menorca. 101 



of the narrowest part of tlie sliaft is 184 mm., -whilst this measuremont 

 for the larp^fist Aldabran specimen given by Dr. Giinther is 160 mm.^ 

 Mr. Tagliaferro is of opinion that his examples indicate the presence 

 of another race, for which he suggested the name of T. rohtistissima 

 in a letter to tlie Daily Malta Chronicle for February 17, 1913. This 

 makes the third species of large land tortoise to be differentiated and 

 described from Malta. 



In Chelonians actual size alone is not a very important 

 characteristic. Like those from Malta, the Menorcan specimens 

 sliow an enormous range in size ; one reason to account for this may 

 be the former very great abundance of reptiles in the island. Tliis 

 suggestion is further borne out by the originally large area of the 

 deposits in which the remains were found. The extreme variability, 

 both in actual size and relative measurements, that obtains in the 

 remains of the gigantic tortoises from Mauritius and Ilodriguez has 

 already been pointed out by Professor A. C. Haddon.^ 



Owing no doubt to the great reduction made in the numbers of 

 the existing races of gigantic tortoises since their discovery in the 

 Galapagos Group and islands of the Indian Ocean, chiefly on account 

 of the custom of passing vessels taking great quantities on board, 

 it seems to have become a widely accepted axiom that these creatures 

 are too defenceless to exist except in isolated areas where they would 

 not be subject to the attack of other large animals. It seems that this 

 may hold good in the case of civilized and perhaps semi-civilized man, 

 but not with regard to large caruivora, as for instance ilr. Hay writes : ' 

 " The large Testudinidse of North America, from the Lower Eocene 

 to the Pliocene, were exposed to the attacks of large carnivora." He 

 continues to say: "... Dr. Leidy has figured the claw phalanx* 

 of a species of Testudo found in Pleistocene deposits in Hardin County, 

 Texas. The individual must have been one of great size. We do not 

 know why some of the Pliocene gigantic tortoises should not have had 

 descendants in the Quaternary worthy of accompanying the great 

 mammals of that period." Further, it may be remembered that 

 although the only remains of large carnivora obtained from the Malta 

 caves was a single indeterminable tooth. Dr. Falconer," in writing 

 to Admiral Spratt, mentioned that "There are numerous bones in 

 your Zebbug cave collection that are fiercely gnawed, and evidently 

 by a large predaceous carnivore". 



It seems probable that the extinction of a race of giant tortoises 

 Avould be more easily brought about by the continued and wholesale 

 destruction of the eggs and young, as, for instance, it has been recorded 

 b}' Mr. Beck® that "On Albemarle the dogs and cats undoubtedly 

 eat a great many young tortoises ". 



The freedom of the adults from attack has also been brought 

 forward as the cause of the thinning of the shell in some of the races 



^ Gigantic Land Tortoises in the Collection of the British Museum, London, 

 p. 31, 1877. 



" Trans. Linn. Soc, ser. II, Zoology, vol. ii, p. 157, 1881. 



^ The Fossil Turtles of North America, Washington, p. 373, 1908. 



■* Contrib. to the Extinct Vert. Fauna W. Territories, 1873, pi. xxxiii, fig. 21. 



^ Pal. Mem. London, vol. ii, p. 301, 1868. 



" Novitates Zoologicce, vol. ix, p. 379, 1902. 



