let MARINE BIOLOGY OF THE SUDANESE RED SEA. 
Reports on the Martine Brotoay of the SupaANEseE Rep SeaA.—IV. The 
Recent History of the Corat Reers of the Mid-West Shores of 
the Rep Sea. By Cyrit CrossLanb, M.A., B.Sc., F.Z.S.  (Communi- 
cated by Prof. W. A. Herpmay, HERES oes laSs) 
(PLates 1 & 4.) 
[Read 2nd May, 1907.} 
CONTENTS. 
Pp 
age 
General Description of the Coast ..........-..... ecules OS eo 14 
BvidencesvoteMleyatroncc. ye emene reer ies eerste r tk sel cie een nee 17 
Its regularity—Corals and material of reefs remaining in position. 
Raised Atoll of Tella Tella Suraya. 
The Living Reefs—Fringing, Scattered, Barrier .............-.-++.. 19 
Mine Romonaynomn Or Comune oc coscacccocnorpcovasccvG0euaenagueos 24 
(Oloravel rUiSpVoyVice eaetee Oks 2 een Ree eyo ena Sin Acs wi olo iota Suen RGR ey CO B Om bo OD c 26 
GENERAL DESCRIPTION OF THE COAST. 
Tue remarkable parallelism of the sides of the Red Sea “ Rift Valley ”-is 
varied on the west by three prominent points, Ras Benas, Ras Elba, and Ras 
Rawaya (see Map, fig. 1, p.6). Between Ras Rawaya and Suakim the 
coast-line is, in the main, very regular, but it bends eastward again at 
Trinkitat, and is broken by some large bays about Agig. 
As is well known, the sides of this trough are composed of ranges-iof 
mountains of granite and other crystalline rocks remarkable for their wild 
and jagged shapes and utter barrenness, while the actual coast is a low 
plain. Except for its seaward border, which is invariably of elevated coral, 
the surface of this plain is composed of alluvial gravel and sand from the 
hills *. In certain localities the plain is divided by ranges of low hills, 
somtimes capped with coral, which rise in the midst of the plain and run 
parallel, more or less, to both sea-coast and mountains f. 
This is the structure of the whole Red Sea coast at least as far south as 
latitude 18° 10’ N., with the exception of the northern part of the Gulf of 
Suez, which is totally different ¢. 
A very striking feature of this coast is the large number of canal-like bays 
or “ Khors” which run into the coast-plain. Reference to the map on p. 6 
shows nine large examples in the space of only 40 miles just north of Rawaya, 
* Artesian borings made by the Public Works Department of the Sudan Government 
two miles inland from Port Sudan show that the same materials extend downwards as far as. 
the borings wert, z. e. to a depth of at least 1000 metres. 
+ As these hills are of special interest I give an enumeration of them and description of 
those I have climbed in a postscript (p. 27). 
{ The crystalline hills are here absent, the coast being formed of high, flat-topped, wall- 
like hills of Cretaceous limestone which rise almost directly from the sea. 
