130 [No. 98 ECONOMIC CONDITIONS tion of mother-of-pearl “ seed ” oysters as an article of food . The Ceylon pearl-oyster is found in the Red Sea, and young specimens are eaten at Suez as a substitute for the true edible oyster, which occurs in certain areas , but is difficult to collect on account of its solitary habits. Experiments have been made with a view to increasing the size and number of these oysters . Observations on the habits of certain shell destroying fishes were also made.

Among other shells of commercial value found in the Red Sea are those of a fish with six fin - like projections ( Pteroceras lambis ), which sells for about £E . 12 per ton ; the pegtop shell (Trochus ) , £E . 15 per ton ; a large kind of clam shell ( Tridacua ), £E . 10 per ton; and many species of cowrie or porcelain shells (Cypreae ), ££. 14 per ton.

Sponges are found off Khor Dongonab, onthe reefs near Suakin, and in other partsof the Red Sea .

Biological conditions are reported as favourable, but the quality of the sponges is not considered so good in the markets as that of sponges from the Mediterranean .

Several species of sea cucumber, used in the preparation of bêche-de-mer (trepang ) , a favourite article of diet among Chinese and other Eastern peoples , are to be found in the Red Sea, but there is no export from the Sudan . Black coral (yusur), used for ornamental purposes, is fished for. Edible and shell turtles occur insmall numbers.

(4) MINERALS In general , the surface of the Anglo -Egyptian Sudan north of 12° north latitude consists of old sedimentary sandstones and clays overlying a bed of older crystal lines , which are an extension of the underlying rocks of the Abyssinian plateau . These crystalline rocks chiefly granite , gneiss , and schists — appear on the surface in many places, especially on the east and south frontiers, and in Kordofan . They form the backbone of the principal mountain ranges and outcrop