54 
THE EACES OE THE MASCAEENES. 
The Eodriguez Tortoise differs from the Mauritius and Galapagos Tortoises by the 
more slender build of all the various parts of its skeleton ; its neck must have been 
capable of still greater flexion, as is evidenced by the deep postapophysial impressions 
or actual perforations of the cervical vertebrse. Although careful comparative mea- 
surements show beyond doubt that this Tortoise had longer limbs and a longer neck 
than even some of the Galapagos Tortoises, yet, taking also into consideration the extreme 
thinness and fragility of its carapace, we must infer that this general slenderness of the 
bones must have been partially due to the same cause, probably a diminished supply of 
the calcareous salts, or a diminished power of assimilation of them. 
The bones collected by the naturalist of the Transit-of- Venus Expedition belonged 
to several hundred individuals ; and there are in some cases as many as forty specimens 
of one and the same bone in the collection ; yet no variation in structure equivalent to 
that observed among the Galapagos, Aldabra, and Mauritius Tortoises could be detected, 
so that evidently in this small island there was room for one species only. The only 
variation which is worth recording is one which can be explained as a sexual diflference, 
the female having been of a smaller size and somewhat stouter form than the male, 
as is the case in the other Gigantic Tortoises. 
Bones far exceeding in size the majority of their kind are not rare, and prove that 
the Rodriguez Tortoise was quite equal in bulk to Testudo elephantina, many (probably 
male) individuals having had a carapace feet in length. From Dumeril and Bibron's 
descriptions we learn that the scutes were perfectly smooth or nearly so, and that the 
shell of the adult was black, whilst the young were of a lighter brown colour, the 
sternum being dotted with yellow. 
Lescription of the Osseous Remains. 
Skull (Plate XXIII. fig. C).— The skulls of twenty-four individuals of various ages, 
in a more or less imperfect condition, have been collected. They show very little 
variation beside that which is simply due to age. Two of the largest and most perfect 
are respectively 4^ and 4^ inches long, measured from the intermaxillary to the occi- 
pital condyle, and 3| and 3 inches broad at the widest part, viz. between the tympanic 
processes. 1. The frontal region is very broad and flat transversely, sloping in a more 
or less strong curve towards the nostril, its greatest width (in front of the postfrontals) 
being as much as, or not much less than, one half of the greatest width of the skull. 
2. Only the foremost part of the parietals forms a flat surface, the remainder being 
compressed into a crest that passes into the long and narrow occipital spine, which 
rises scarcely above the level of the upper surface of the skull. 3. The tympanic case, 
with the mastoid, is produced backwards, the hind margin of the paroccipital forming a 
rather strong curve. 4. There is a shallow impression or hollow in front of the 
occipital condyle. 6. On the front margin of the temporal fossa, corresponding to 
the suture between parietal and tympanic, and directly in front of the foramen caro- 
