178 



A. LEITH ADAMS ON MALTESE LAND-TORTOISES. 



rivalled in proportions the largest living and extinct land tortoises 

 of the Mascarene and Galapagos Islands. Several pieces of plates 

 show thicknesses varying from 2 to 20 millimetres, but present no 

 further characters of importance, all being extremely fragmentary. 

 They establish, however, much variability in the dimensions of their 

 owners, which is confirmed by a study of the following bones. It 

 may be observed that the denser outer dermal layer of several frag- 

 ments belonging to the small Chelonians is marked by numerous 

 white specks, such as are seen on the epidermis of the Lutremys 

 europcea, with which, it will be seen, the humerus (Plate VI. fig. 6) 

 and femur (Plate VI. fig. 5) agree in all particulars. 



Vertebral Column. 



- A cervical vertebra from Mnaidra Gap and a caudal vertebra from 

 Benghisa Gap belong to gigantic land- tortoises. Both are referred 

 to in my previous communication *, which was drawn up in Malta 

 during the progress of the explorations, when I had not the means 

 of making comparisons. 



The cervical vertebra is much injured : the anterior portion is 

 lost, leaving the posterior condyle and posterior zygapophyses, with 

 a portion of the neural arch ; the last, however, is distorted and 

 crushed. Enough remains, nevertheless, to show that it is a fifth 

 cervical. As compared with the same bone in an individual of the 

 large Galapagos form described by Dr. Giinther f under the name 

 of Testudo elephantopus of Harlan, the above represents not only a 

 larger but also a more robust tortoise; and as the latter character 

 will be seen to prevail in all the large Chelonian remains in onr 

 united collections, I propose to distinguish this (the largest) species 

 of tortoise from the others by the name of Testudo robusta. As far 

 as the injured condition of the fossil will allow, the following com- 

 parisons have been made between it and the typical specimen of T. 

 elejjhantopiis, as given by Giinther. In both, t he neural crest 

 divides and proceeds along the dorsal aspects of the posterior zyga- 

 pophyses, thereby forming a shallow triangular space between them. 

 The following measurements are procurable : — 



Breadth of condyle 



Thickness of condyle 



Greatest breadth of zygapophysis 

 Least breadth of centrum 



T. elephan- 

 topus. 



T. robusta. 



millim. 

 33 



millim. 

 37 



20 



26 



10 



18 



20 



22 



* Quart. Journ. Geol. Soc. vol. xxii. p. 595. 



t Philosophical Transactions, vol. clxv. 1875, p. 251. 



