THE GI&ANTIC LAND-TOETOISE OF EODEIGUEZ. 
55 
tidis externse, there is a large, prominent, concave, rough tuberosity for the insertion of 
a portion of the temporal muscle ; exteriorly a narrow and deep groove separates this 
tuberosity from the zygomatic arch ; inside of it runs a sharp ridge in an oblique direc- 
tion from the tympanic condyle to the upper limit of the temporal fossa. This ridge 
separates the foramina by which the nerves and blood-vessels that leave the cerebral 
cavity by the foramen sphenoidale (portions of the nervus quintus and carotis cerebralis) 
issue from the substance of the bone. These external foramina vary somewhat in 
number and position ; but there are generally two behind and a smaller one in front of 
the ridge. 6. Tympanic cavity large, but somewhat constricted in the interior portion 
of its entrance ; the outer tympanic rim has a rather irregular outline, not well defined 
in front, and with a deep and rather broad notch in the posterior part of its circum- 
ference for the passage of the Eustachian tube. 7. The columella is attached to and 
rests upon a long, nearly straight and rather sharp ridge, which runs from the notch 
mentioned to the stapedial foramen. 8. The posterior wall of the inner tympanic 
cavity, which in fresh examples is formed by cartilage and an open space in the pre- 
served skull after maceration, is but limited in extent, about one seventh of the area 
of the tympanic opening. 9. The front margin of the intermaxillary projects beyond 
that of the frontal, the nasal opening being about as wide as long, 10. Although the 
position of the choanal is advanced forwards, yet on the palatal view of the skull the 
greater portion of them may be seen uncovered by the alveolar lamellse of the maxil- 
laries ; the front extremity of the vomer which separates the choante is very narrow and 
slender. 11. The foremost part of the intermaxillary is hollowed out below and ver- 
tically bent downwards to form the truncated beak. The suture between the inter- 
maxillary and vomer is immediately behind the inner angle of the alveolar edges of the 
maxillaries. 12. Palatal region rather deeply concave and broad, a longitudinal 
median crest being scarcely indicated. The distance between the foramina palatina is 
much less than that between these foramina and the anterior extremity of the vomer. 
Outer pterygoid edge rather elevated and sharp. 13. Anterior surface of the tym- 
panic pedicle with a moderately deep impression. 14. Lower jaw with a double 
alveolar ridge ; its symphysial portion simply vertical, without a backward expansion 
of the lower margin of the bone. 
Carapace (Plates XXI. and XXII.). — Tolerably complete carapaces of five indivi- 
duals were found ; unfortunately they are of more or less young age, the two largest 
being only 16^ and 21 inches long. Four of them are very similar to one another, 
whilst the fifth and largest, though presenting the same specific characteristics as the 
others, differs considerably in shape. The carapace is distinguished by its extreme 
thinness and fragility, the lateral portions being only 1 millim. thick. Although the 
weather must have had some effect upon the preservation, exposure to it cannot have 
been the only cause, and can only slightly have deteriorated the surface, as the lines of 
impression of the epidermoid plates are distinctly preserved. Another characteristic of 
