28 
THE EACES OE ALDABEA. 
longitudinal axis of the vertebrse. All these characters are indicative of a compara- 
tively shorter neck with lessened power of turning, as we actually observe it in the 
livino" animals, although it must be remembered that the length and mobility of the 
neck of these Aldabra Tortoises is still much greater than in any of the smaller forms 
of the genus Testudo. Most remarkable is the peculiarity in the articulation of the 
third and fourth vertebrae, which in all the Flat-headed Tortoises (from the Galapagos 
as well as Mauritius and Rodriguez) is reversed. 
In the atlas of the younger individual the lateral portion of the neural arch (column) 
is very broad, considerably broader than the zygapophysis, which is rather shorter than 
that part of the bone which forms the roof of the arch. These parts are separated 
from one another by less-deep constrictions in the adult specimens, the lateral portion 
being nearly as broad as the zygapophysis (Plate X. fig. A). The centrum (odontoid 
process) is as broad as long in the adult, and broader than long in the young, with 
oblique articular surfaces, two in front and one behind. 
In the second vertebra (Plate X. fig. B) the neural arch is somewhat compressed, 
provided with a low crest. The third has a condyle in front and behind, the posterior 
being much elongate and reaching beyond the extremity of the zygapophyses (Plate X. 
fio-. C). The fourth, has a glenoid cavity in front and a condyle behind ; there is a 
marked hollow in the neural arch behind the anterior zygapophysis in the adult speci- 
men, which is absent in the young, clearly showing that this peculiarity is developed 
with age. The ffth has a single low median neural crest (Plate XL fig. A), and a deep 
hollow behind each anterior zygapophysis. The sixth has a glenoid cavity in front, and 
a broad, depressed, bipartite condyle behind ; its dorsal surface is much compressed, 
with a short, high, triangular crest, whilst on the visceral surface a lower crest runs for 
about two thirds of its length and bifurcates behind (Plate XII. fig. A). The seventh (bi- 
concave) vertebra (Plate XIII. fig. A) is distinguished by the high crest on its dorsal and 
visceral surfaces; in the middle of the vertebra the neural crest is spht into two 
branches, diverging in the direction of the posterior zygapophyses and leaving a deep 
triangular recess (a) between them. The point of divergence forms a kind of summit (b) 
to this vertebra, which, however, is overtopped by the extremities of the anterior zyga- 
pophyses. The place on the neural arch inwards of and behind each anterior zyga- 
pophysis is not hollowed out, as in the Galapagos and Eodriguez species, and is even 
much less concave than the corresponding portion of the preceding vertebrae. The 
anterior and posterior glenoid cavities are completely divided into a right and a left half 
in the adult, and less completely in the young specimen. The eighth vertebra (Plate XIV. 
fig. A) has a bipartite anterior and single posterior condyle, the posterior zygapophyses 
being curved downwards, to the level of the condyle. 
The measurements of the second to seventh cervical vertebrae are as follows : — 
