4] 
THE EXTINCT RACES OF THE MASCARENES. 
In the introductory part of my paper in Phil, Trans. 1875, p. 253, it has been stated 
that the extinct races of the Mascarenes have a flat cranium, truncated beak, a broad 
bridge between the obturator foramina, and (it might have been added) the fourth 
cervical vertebra biconvex. They were thus sharply and structurally differentiated 
from the Tortoises of the Aldabra group ; but there was no common character apparent 
by which they could be distinguished from the Tortoises of the Galapagos. Such a 
character can now be pointed out since we obtained more or less complete carapaces 
from Mauritius and Rodriguez : it consists in the apparently insignificant absence of 
the suture which divides, in most Land-Tortoises, the gular plate of the sternum into two 
longitudinal halves. I have besides been able to ascertain that the nuchal plate is in- 
variably absent in all Mascarene Tortoises. Thus, then, what for many years past and 
at the beginning of these researches seemed to be an almost hopeless task, and what, 
without the recent explorations instituted in Mauritius and Rodriguez, would have 
remained an insoluble problem, has found a most simple solution, and there will be 
in future no difficulty in determining the origin of those carapaces which for genera- 
tions have been kept in museums, and whose history was veiled in obscurity or for- 
gotten long ago. We may state : — 
1. That the specimens with a nuchal plate {and ivHh double gular) came from 
Aldabra ; 
2. That the specimens loith single gular [and without nuchal) came from the Masca- 
renes ; and 
3. That the specimens without nuchal and with double gular are Galapagos Tortoises. 
With the aid of this key we can now not only refer various species based by older 
authors on more or less perfect specimens to their proper geographical division, but also 
identify them with such as have been distinguished from the osseous remains only. 
A. The Gigantic Land-Tortoises op Mauritius. 
The materials in the British Museum on which the following remarks on the Tor- 
toises of Mauritius are based are the following : — 
1. A series of limb-bones and portions of the cranium from the " Mare aux Songes," 
G 
