94 Correspondence. 
I conceive it can no longer be affirmed that Cycloid fishes did not 
exist previously to the Cretaceous epoch.— Yours, &c., 
C. B. Ross, F.G.S. 
Great Yarmouth, June 14th, 1864. 
We append the following note in reply, obligingly furnished by Mr. W. Davis. 
Eprr. 
Since Mr. Rose examined the slab in the British Museum (referred 
to in the above letter), another and a much better specimen has been 
acquired from the same locality, which, in addition to many scales 
in their natural position, exhibits portions of the jaws, with teeth 
having a Saurotd character. 
As several species of true sauroid fishes, having similarly marked 
scales, occur in the Upper Oolite (Lithographic stone) of Solenhofen, 
it is probable that these imperfect specimens from our Kimmeridge 
Clay may prove to belong to a new genus of the same family. 
Thrissops formosus and Megalurus lepidotus may be quoted as 
examples of Ganoid fishes having scales with Cycloid ornamentation. 
Agassiz describes the last-named species as having scales somewhat 
resembling those of the Carp, and gives an illustrative figure in 
pl. L1.8 vol. ii. of his ‘ Poissons Fossiles.’ W. Davies. 
CAN THERE BE A RAINLESS DISTRICT? 
To the Editors of the GEOLOGICAL MAGAZINE. 
In the first article of your first number I hail the words ‘a whole- 
some scepticism. Is the scepticism of the title of this letter 
‘wholesome ?’ I consider a ‘rainless district’ to be an impossibility. 
In Professor Desor’s article on the Sahara, the ‘rainless district’ is 
not mentioned. But water is mentioned in rivers, in pools above 
ground, and in ‘sheets’ below ground, and ‘ moist beds’ at a depth 
of eight or ten metres. A ‘rain of several days’ is mentioned, and 
the ‘ Desert of Erosion’ is described as the result of ‘rain and rivers.’ 
As a matter of fact, I would ask through the medium of your 
Journal, does rain fall on the Sahara, or does it not? Iask the 
same question with regard to Egypt. According to the ‘Star’ of 
February 22, 1857, the passengers by the ‘Indus’ reported ‘a fall of 
snow at Cairo.’ In May 1860 part of the railroad between Cairo 
and Suez was washed down by heavy rains, and the travellers from 
India were stopped for two days. ‘To the north of this district, in 
the desert of El Tyh, Mr. Lowth (‘ Western Footsteps in Eastern 
Climes’) gets frequently soaked with rain. He describes the whole 
surface as scored with channels of torrents tributary to the Wady 
Legaba and El Arish. In one of these channels he found a river 
rushing, twenty yards wide, and three or four feet deep. And he 
was obliged to wait, like the rustic, dum defluat amnis. Now, this 
is no accidental affair, for the El Arish is the Torrens Agypti, and 
has therefore carried torrents across Arabia Petreea to the Medi- 
terranean for at least 2,000 years. Again, in descending the El 
Araba to the Dead Sea, Mr. Lowth mentions ‘marks of the rush of 
waters, long, deep, sharp clifts in the ground, and water-worn stones 
and torn shrubs half uprooted ia torrent-beds. Now, Keith John- 
