1 1 10 CLASS REPTILIA. 



in the middle (fig. i o 1 7 bis). Usually the caudal shield is single, 

 but it may be divided. The ribs have no heads for articulation with 

 the vertebrae. The forms described as Manuria and Colossochelys 

 may be included in this genus, which comprises a large number of 

 species. Exclusive of the Jurassic so-called T. Strickland!, which 

 has been already mentioned under the head of Protochelys, the 

 earliest occurrence of the genus appears to be in the Upper Eocene 

 Phosphorites of France ; it is, however, not certain that the form 

 from these deposits may not be referable to one of the American 

 genera. A marginal in the British Museum indicates an individual 

 about 30 inches in length. T. gigas, of the Miocene of Haute- 

 Loire, is a still larger form ; and species of large dimensions also 

 occur in the Lower Miocene of Allier and the Middle Miocene of 

 Gers, as well as in the Pliocene of France and Greece. 



The huge T. (Colossochelys) atlas, of the Pliocene Siwaliks of India, 

 was one of the earliest of the large extinct forms brought to the notice 

 of science, although its size has been greatly exaggerated. It appears, 

 indeed, that the length of the carapace was about six feet, or one-third 

 greater than in T. elephantina, of the Galapagos Islands. This species 

 is remarkable for the great development of the epiplastral bones, which 

 formed a pair of horn-like processes ; and is also noteworthy for the 

 anchylosis of the three bones of the pelvis into an innominate bone. The 

 skull, which probably belongs to this species, resembles in structure the 

 skulls of the recent giant tortoises of Aldabra. The carapace had no 

 nuchal shield, the caudal shield was divided, and the limbs were 

 covered with bony ossicles, as in the existing T. emys of India, to which 

 this form was probably allied. The large T. fterpiniana, of the Pliocene 

 of France, in which the depressed carapace measures nearly four feet in 

 length, and the limbs were likewise covered with dermal ossicles, was 

 probably also nearly allied. An unnamed species, from the Pliocene of 

 the Siwalik Hills, has a skull resembling that of the Galapagos tortoises 

 (fig. 1017 bis); which are characterised by the backward extension of the 

 opisthotics. We also find in the Siwaliks T. Cantleyi characterised by 

 its small epiplastrals ; and T. pimjabiensis, which appears to have been 

 a form allied to the smaller existing Indian T. emys. Remains of giant 

 tortoises also occur in the Pleistocene cave-deposits of Malta. 



Finally, we must not omit to briefly mention the giant tortoises of the 

 present epoch, which, it appears, have been driven from the continental 

 areas by the competition of the higher types of life to seek refuge in 

 islands, where they attained an extraordinary numerical development, till 

 their haunts were invaded by man. These tortoises formerly existed in 

 great numbers in the islands of the Aldabra group, lying to the north-west 

 of Madagascar ; in the Mascarenes, which comprise Mauritius and Rodri- 

 guez ; and also in the Galapagos, or " Tortoise-Islands," which lie off the 

 coast of South America. The Aldabra Tortoises are characterised by 

 their deeply excavated palate, short opisthotics, and the presence of a 

 nuchal and of double gular shields. Some of them were living in the 

 year 1877. In the Pleistocene of Madagascar remains of two very large 

 species have been found, both of which present the characters of the 

 Aldabra forms. The Mascarene species have no nuchal shield, and only 

 a single gular ; and the whole of them have been exterminated by human 



