*A paper read at the Annual Congress of the South African Association for the Advancement of Science held in Bulawayo in July 1953. 1. An anomalous band of pectoralis major is descriptionbed in a South Mrican Negro. 2. It arises chiefly from the 6th rib and forms the inferior edge of the anterior axillary fold. 3. On reaching the arm, the muscular band turns distally and is inserted obliquely into a tendon at its lateral margin. 4. The tendon fuses about 3 inches above the medial epicondyle of the humerus, with an anomalous fibrous cord. The latter is attached above to the mam tendon of the pectoralis major and to the lateral lip of the bicipital groove and below, to the medial epicondyle of the humerus; the fibrous cord is regarded as an accessory tendon of pectoralis major. 5. The anomalous band of pectoralis major differs in several respects from the previously descriptionbed sterno-chondro-epitrochlearis and chondro-epltrochleans muscles. As it arises only from ribs, it is considered more appropriate to call the anomaly descriptionbed in this paper musculus costo-epitrochlearis. 6. Pectoralis major muscle is fused with the deltoid, and the deltoid, in turn, with the brachialis and the long head of biceps. The latter anomalies suggest a tendency for pectoralis major to extend its purchase distally in the arm.