264 
DE. A. GUNTHER ON GIGANTIC LAND-TORTOISES. 
one half of the length of the maxillaries ; their foremost portion is deeply hollowed out 
below, and vertically bent downwards to form the truncated beak. The suture between 
the intermaxillary and vomer is immediately behind the inner angle of the alveolar 
edges of the maxillaries. 12. The palatal region is much less concave than in the 
Aldabra Tortoise, and divided along its middle by a high longitudinal crest. The 
triangular space of which the foramina palatina and the anterior extremity of the vomer 
form the points is nearly isoscelous in shape, in accordance with the generally short 
longitudinal axis of the skull. Outer pterygoid edge (f) rather elevated and sharp. 
13. Anterior surface of the tympanic pedicle deeply excavated. 
14. Lower jaw with a double alveolar ridge; its symphyseal portion simply vertical, 
without a backward expansion of the lower margin of the bone. The parts of the 
angular and coronoid which face each other are closely approximate, leaving only a 
narrow cleft between them. Upper margin of the angular deeply excised. 
The cervical portion of the vertebral column is characterized by its relatively great 
length . All observers were struck by the length of the neck, which the animal is in the 
habit of erecting so that the head is raised above the level of the shell. A living animal 
now before me can turn its head in this position to the right or left, reminding one of 
a Cobra rising in a posture of defence. This slenderness of the neck is not due to an 
increase in the number of vertebrae (which is constant in Tortoises as in Mammals, and 
limited to eight), but to their elongated shape. In T. elephantopus they are not quite 
so slender as in T. rodericensis, but much more so than in the species from Aldabra. 
Also the spinal canal is narrower than in this latter round-headed form. The crests of 
the dorsal as well as visceral surface are well developed, and sometimes accompanied 
by low additional crests. All the articulary processes diverge comparatively but little, 
and those which in the Aldabra species are nearly perpendicular to the longitudinal 
axis of the vertebra, are oblique and much depressed in T. elephant opus. 
In the atlas (Plate 40. fig. A) the lateral portion of the neural arch (column) is very 
much constricted, not broader than the zygapophysis, which is elongate and considerably 
longer than that part of the bone which forms the roof of the arch. The centrum 
(odontoid process) (a) is a rhombohedral body. 
In the second vertebra the neural arch is remarkably compressed and elevated, also 
provided with a high neural crest. The third has a condyle in front, and a glenoid 
cavity behind*. The fourth is biconvex. The fifth (Plate 40. fig. C) has a glenoid 
cavity in front and a condyle behind ; its median neural crest is low, and accompanied 
on each side by two other crests which diverge in the direction of the posterior zyga- 
pophyses. The sixth (Plate 40. fig. D) has a glenoid cavity in front and a condyle 
behind ; its dorsal surface is flat, without crest, whilst on its visceral surface a low crest 
is evenly continued along nearly the whole length of the vertebra. The seventh biconcave 
vertebra (Plate 41. fig. B) is distinguished by the high crest on its dorsal and visceral 
* We shall see in the following part of this essay that these articulations of the cervical vertebrae are some- 
what modified in the Aldabra species. 
