276 
DR. A. GUNTHER ON GIGANTIC LAND-TORTOISES. 
Skull. — The skull of the adult male (Plates 37-39. fig. B) is 3^ inches long, measured 
from the intermaxillary to the occipital condyle, and 2^ inches broad in its widest 
part, viz. between the zygomatic arches. In general appearance it has a great resem- 
blance to the skulls of young examples of the larger species ; yet nearly all the sutures 
have disappeared, so that the example is evidently a fully adult individual. It is thus 
another instance of a w r ell-known fact, viz. that often small species retain through life 
the juvenile characters of their larger and more fully developed congeners. The skull 
is conspicuously more similar to that of T. ei^lii'p'pium than to those of the first two 
species, as will be seen from the following notes : — 1. The frontal region is flat, very 
broad, passing into the very short snout, its greatest width (in front of the postfrontals) 
being rather more than one half of the distance between the tympanic condyles. 2. The 
occipital crest is comparatively short, pointed behind, and scarcely rising above the level 
of the surface of the skull. 3. The tympanic case, with the mastoid, is but little pro- 
duced backwards, the hind margin of the paroccipital (a) being nearly straight. 
4. There is no hollow in front of the occipital condyle, the space (b) between the con- 
dyle and basisphenoid gently shelving downwards towards the latter. 5. On the front 
margin of the temporal fossa, in front of the foramen carotidis external, there is a broad 
concave prominence ( c ) for the insertion of a portion of the temporal muscle ; no groove 
separates this prominence from the zygomatic arch ; or, in other words, the tympanic 
cavity is not constricted in front. 6. Tympanic cavity of moderate size, the posterior 
portion being particularly small : the outer tympanic ring is subcircular ; the notch (e) 
for the passage of the Eustachian tube rather narrow, but deep. 7. The ridge which 
runs from this notch to the stapedial foramen, and to which the columella is attached, 
is rather low and trenchant. 8-11. The points noticed under these numbers in the 
descriptions of the skulls of T. elejohantojpus (p. 263) and T. ephippium (p. 273) are exactly 
the same in the present species. 12. The palatal region is moderately shallow and not 
very broad, but the outer pterygoid edge is expanded as in T. ephippium. The distance 
between the foramina palatina is conspicuously less than that between one of these 
foramina and the anterior extremity of the vomer. 13. Anterior surface of the tym- 
panic pedicle with a deep impression. 14. Lower jaw with a double alveolar ridge ; its 
symphyseal portion is 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. Upper margin of the angular not excised*. 
* With regard to the skull of a very young example in the British Museum, I still hesitate to refer it to this 
species. There cannot be any doubt that it belongs either to T. ephippium or to T. microphyes , having the 
pterygoid edge expanded in the manner by which those two species are so well characterized. But the occi- 
pital spine is more produced backwards than I should have expected to find it in the young of T. microphyes , 
the adult of which has this process comparatively short. However, the outer tympanic rim has exactly the 
suhsemicircular shape of that species, and not the ovate outline of T. ephippium. 
