282 
TERTIARY VERTE15RATA OE THE EATlJM. 
of Bournonclc-St.-rierro (Allier), differs from the present species in the form of the 
plastron, the anterior lobe of which narrows gradually forwards to a point; it also 
differs in the grc'at convexity of the carapace, the other characters of which 
unfortunately have not been described. 
Another Tertiary giant Tortoise, with which T. ammon may be compared, is 
T. j)crj)in?(ina, described by Deperet and Donnezan^ from the Lower Pliocene of 
Uonssillon. This species also attained a very large size, one shell measuring 
120 cm. in length. The chief points in which it differs from T. ammon are: — 
(1) the caraj)acc is much less convex and is smooth; (2) there is no nuchal; (3) the 
])lastron, ihongh somewhat similar posteriorly, differs anteriorly in narrowing more 
rapidly and in not having the epiplastral prolongation (which, however, may be a 
sexual character). 
T. Icheronis, Deperetf, from the Miocene of Mt. Leberon, is very similar to 
T. perpiniana, but still larger, the shell attaining a length of 150 cm. It has also 
more slender epiplastra and xiphiplastra, and therefore approaches the present species 
in these points rather more nearly than does T. perpimana. The gigantic extinct 
'Tortoises of India, such as T. atlas, seem to be closely similar in many ways to these 
European Tertiary forms, particidarly in the absence in most of them of the nuchal 
shield — a charactei’ which distinguishes them from the present species. 
When the original description of this species was written the presence of a nuchal 
shield had not been recognised, and consequently it was considered that it was more 
nearly related to the European and Indian Tertiary forms than now appears to be 
the case. So far as the evidence goes now, it seems that the nearest relationship is 
with the Aldabra and Mascarene types and perhaps with some of tlie Indian forms, 
in which a nuchal is also present. 
Several more or less nearly complete humeri of Land-Tortoises have been found 
in the same beds as the shells, and though none of them are large enongh to have 
belonged to an animal of the size of the type specimens of T. ammon or T. headnelli, 
nevertheless they may be regarded as probably referable to small specimens of one 
of these species or of T. isis. The shaft forms a strong sigmoid curve. The ulnar 
and radial crests are both strongly devedoped and make a very acute angle Avith one 
another ; they are separated by a deep fossa : the ulnar crest rises consideral)ly above 
the head, Avhich is an elongated oval in form. The dorsal surface of the upj)er 
part of the shaft is marked by a strong ridge Avith a deep groove on its iniu'r side 
for the insertion of muscles. The middle of the shaft is comparatively slender and 
is triangular in section. 'I'hc distal expansion is not so great as in most of the large 
Land-Tortoises, e. g. T. (ji<janfca. The ectcpicondyle is rather small : there is a 
hmg and deep ectepicondylar groove Avhich perforates the bone at its lower luid. 
■* Coiiii)te.s Rondus, vol. cv. (1837) p. 1275; also Mt'm. Hoc. Geol. France, Mean 3 (1890) p. 140. 
t Couij)tes Rendiis, vol. cx. (1890) p. 915. 
