TESTUDINID&. 373 
America, taking a northwestern direction, they past into Asia over the bridge of land which 
occupied the position of Bering Strait. Passing westward they entered Europe. Others 
spreading southwestward peopled India and the strip of land which connected the latter 
country with Africa, and which now, greatly deprest, is represented by Madagascar and 
various groups of islands. From this land they entered Africa itself. 
The living Testudinida which have been designated as “ ojgantic tortoises” all belong to 
the genus Testudo. The species of Hadrianus of the Eocene were worthy of being called 
gigantic. That the gigantic forms, living and extinct, may, in some cases, have been derived 
from small species and that some of the smaller modern species are the descendants of extinct 
gigantic ancestors, are possibilities. Within historical times gigantic tortoises have lived only 
on islands, where there are no large carnivorous mammals. On the other hand, the large 
Testudinidz of North America, from the Lower Eocene to the Pliocene, were exposed to the 
attacks of large carnivora. 
As remarkt by Mr. R. Lydekker, the gigantic tortoises became extinct on all the conti- 
nents at the close of the Pliocene. This appears to be true of North America, since the 3 species 
ee 
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Fic. 471.—Testudo sumeirei. View of living animal. After Rothschild’s figure, greatly reduced. 
/ Ss a 5 : 
recorded from the Equus beds are all of moderate size. Nevertheless, Dr. Leidy has figured 
the claw phalange (Cont. Extinct Vert. Fauna West. Terrs., 1873, pl. xxxiil, fig. 21) of a species 
of Testudo found in Pleistocene deposits in Hardin County, Texas. The individual must 
have been one of great size. ‘This phalange 1s now in the American Museum. We do not 
know why some of the Phocene gigantic tortoises should not have had descendants in the 
Quaternary worthy of accompanying the great mammals of that period. 
Fig. 470 represents Testudo sumetre: Sauzier, a gigantic tortoise living in Port Louis, 
Mauritius. This figure is reproduced from a plate publisht by the Hon. Walter Rothschild 
(Novitates Zoologica, 1, 1894, plate x1) over the name Testudo indica. This tortoise was men- 
tioned in a treaty made in 1810. The length of the carapace is 40 inches (1015 mm.); that of 
the plastron, 28 inches (711 mm.). 
ANALYSIS OF GENERA. 
A. FEpiplastral lip projecting abruptly from front of carapace. 
a. Neural bones hexagonal. Eocene species. . . nen. ; Hadrianus 
aa. Usually some octagonal and quadrangular neurals; Oligocene to Recent species T estudo 
AA. Fpiplastral lip not projecting abruptly or far beyond gulo-humeral sulci. 
b. Epiplastral lip not thickened backward above; Bridger 2 Achilemys 
bb. Epiplastral lip thickened backward above; Oligocene Stylemys 
Genus HADRIANUS Cope. 
Testudinide with the plastron extensively united to the carapace by suture; with short 
axillary and inguinal buttresses, the latter of which ascend within the sixth costal plates; no 
plastral hinge. Epiplastral lip strongly developt; entoplastron wholly in front of the pectoral 
