10 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
commoner have turned up again in the Red Sea, as have many of those 
conspicuous forms which are at once recognizable by their colour or tubes. 
Plant life resembles that of Equatorial Hast Africa, in that most of the 
species are the same, but occur in different proportionate quantities. The 
absence of coral on the East African reefs is correlated with the vast 
quantities of the marine phanerogam Cymodocea ciliata, Bhrenb., which there 
occupy the spaces here covered with coral, but even on mud or sand-areas 
this species is not often met with on the Red Sea coasts. The true seaweeds 
are the same, but again there is far less ground suited to Halimeda spp., 
which are consequently less frequently met with and then in less abundance. 
On shore Mangroves are absent, perhaps because there is no tidal action 
to plant their floating embryos. Its companion Jussieua, with its aerial 
peg-like roots, is frequently found, but not often in large numbers. 
The salt pools found here and there on these arid coasts soon evaporate 
to a slush of salt crystals, and in these a red microscopic alga flourishes to 
such an extent as to colour the whole pool. Whether the name ‘“ Red Sea” 
is given from this alga or from the pelagic form which makes a scum as if 
of iron rust over large areas of the sea occasionally during calms, or from 
the brown Xeniidee which carpet the harbour sides, is indeterminable; any 
one of the three is a striking phenomenon, the first being obvious to shore 
dwellers, the second to sailors. Perhaps after all, the name was given by 
landsmen who noted the prevalence of red colour in the hills which border 
the sea throughout its length. 
Reports on the Marte Bronoey of the SuDANESE Rep SeA.—III. Note 
on the Formation of the SHORE-CLIFF near ALEXANDRIA. By 
Cyrit Crosstanp, M.A., B.Se., F.Z.8. (Communicated by Prof. W. A. 
Herpmay, F.R.S., P.1L.S.) 
(PLATES 2 & 3.) 
[Read 2nd May, 1907. | 
THE Coast of the Delta is in the form of an are of a circle except on its 
west side, where it runs almost in a straight N.H. and S8.W. line from 
Alexandria to Abukir. These two sections of the coast differ markedly, the 
former having a very low and sandy shore generally backed by swamps or 
lakes, the delta being in process of extension, the latter being bounded by low — 
cliffs due to the rapid erosion of the land -by the sea. (See Plate 2. figs. 1 & 3.) 
The cliffs, with an exception to be noted later, are of the softest material 
throughout, yet always nearly vertical; a fact the significance of which one 
would have supposed could not have escaped the notice of the builders of the 
