392	THE EMPTY QUABTER
From the same deposit I described the pelvis of an Ostrich to
which I gave the name Struthio wimanL The egg-shell fragments
of the Pliocene Ostrich, which was very considerably larger than
the Recent Ostrich, averaged 2-6 mm. in thickness. Having been
weathered out of clay they had undergone little or no erosion from
atmospheric agents, whereas the Arabian egg-shell fragments were
considerably sand worn; so that we may surmise that the latter
fragments were originally much more than 3-0 mm. in thickness;
from which I conclude that Psammornis must have been, at
least, half as large again as the Recent Ostrich.^1
I may add that the eggs of the Northern African Ostrich (S.
cameliw) range, according to my measurements, taken with a
Vernier scale, from 1-8 mm. to 1*9 mm. in thickness.
^1 In a subsequent letter Dr. Lowe, in answer to enquiries from me, wrote
as follows : (1). It is curious that you raise the question whether Paam-
mornis might really belong to the Aepyornis (or * Roc ') group—a fossil
strathious genus confined so far to Madagascar—because I have already
raised this question (Proc. Zool. Soc., 1928).
Lambrecht considers this hypothesis to be supported by the discovery
of a fossil bone (the tarso-metatarsus of a three-toed Struthionid) in the
Qligocene beds of the Fayum, to which he has given the name of Stromeria
There is, however, in the present state of our lack of knowledge always
the question: What are the relations between Psammornis and the
Pliocene Struthio wimani of China ? Therefore I should not like to commit
myself definitely to the idea that Psammornis could be referred to the
*Roc.' It is an interesting speculation. Of course it is not definitely
proved that the fabulous ' Roc * or * Rue * was founded on the huge
Madagascar Aepyornis, but I believe there can be little doubt that it
was so.
(2). Do Ostriches drink water ? I have no practical knowledge derived
from observation, but I do know from Lynes' paper on the birds of North
and Central Darfur (Ibis, 1925, p. 791) that you could have included
birds in general with your Ostrich question.
Lynes says, ' In Northern and Central Darfur, for example, not one of
the birds can possibly get any drinking water, dew included, all the year
round except during the four, five or, at most, six rainy months.' Bates
told me much the same as regards the Southern Sahara—no water, no
dew, and clothes can be dried at night. I imagine then that an Ostrich
could go for an indefinite time without drinking.
Aepyornis, by the way, in Madagascar could have got plenty of water,
and there is a question as to at least one species whether it was not an
inhabitant of the margins of lakes.
Newton in his Dictionary of Birds says, ' Though the Ostrich ordinarily
inhabits the most arid districts, it needs water to drink and, moreover, it
will frequently bathe.* But any bird will if it gets the chance.