By far the most primitive type of the pectoral or shoulder girdle is found in the MONOTREMATA. The scapula (fig. 102, A, 1) is long and recurved, and has only two surfaces, one corresponding to the prescapular[1] fossa, the other to the postscapular[1] and subscapular[169] fossae. The coracoid is a short bone attached above to the scapula and below to the presternum; it forms a large part of the glenoid cavity. In front of the coracoid there is a fairly large flattened epicoracoid (fig. 102, 6); there is also a large =T=-shaped interclavicle (fig. 102, 4), which is expanded behind and rests on the presternum. The clavicles rest on and are firmly united to the anterior border of the interclavicle. This shoulder girdle differs greatly from that of any other mammals, and recalls that of some Lacertilia. [Illustration FIG. 102. _A_, SIDE VIEW, _B_, DORSAL VIEW OF THE SHOULDER GIRDLE AND PART OR THE STERNUM OF THE SPINY ANTEATER (_Echidna aculeata_) × 1. (After PARKER.) 1. scapula. 2. suprascapula. 3. clavicle. 4. interclavicle. 5. coracoid. 6. epicoracoid. 7. glenoid cavity. 8. presternum. 9. second sternal rib. 10. second vertebral rib.] In MARSUPIALS, as in all mammals except the Monotremes, the shoulder girdle is much reduced; there are no epicoracoids and interclavicle, and the coracoid forms simply a small process on the scapula, ossifying from a centre separate from that giving rise to the rest of the bone. The scapula has a long acromion, and a clavicle is always present except in _Perameles_. Unossified remains of the precoracoids are found at either end of the clavicle. The scapula of _Notoryctes_ has a very high overhanging spine, and there is a second strong ridge running along the proximal part of the glenoid border. The shoulder girdle of the EDENTATA shows some very curious variations. In _Orycteropus_ the scapula is of very normal form and the clavicle is well developed. In the Pangolins and Anteaters the scapula is very broad and rounded; there is no clavicle in the Pangolins, and generally only a vestigial one in Anteaters. In Armadillos, Sloths, and Megatheriidae, the acromion is very long and the clavicle is well developed. In the Sloths, _Megatherium_, and _Myrmecophaga_, a connection is formed between the coracoid, which is unusually large, and the coracoid border of the scapula, converting the coraco-scapula notch into a foramen. In _Bradypus_ the clavicle is very small, and is attached to the coracoid, which sometimes forms a distinct bone[170]. In the SIRENIA the scapula is somewhat narrow and curved backwards: the spine, acromion, and coracoid process are moderately developed, and there is no clavicle.