. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. MONOT11EMATA. 377 rower corresponding hone in the Echidna. These hones, which are called the ' epicoracoids' (Jig- 173, A, n n) are joined by their median margin to the stem of the episternal, and by their anterior margins to its transverse branches, which are overlapped by the epicoracoids. The true or acromial clavicle (fig. 173, A, m /«) is a long, slender, compressed, slightly bent bone, continued from the articular cavity at the end of the acromion to near the median line of the episternum, anterior to but parallel
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. MONOT11EMATA. 377 rower corresponding hone in the Echidna. These hones, which are called the ' epicoracoids' (Jig- 173, A, n n) are joined by their median margin to the stem of the episternal, and by their anterior margins to its transverse branches, which are overlapped by the epicoracoids. The true or acromial clavicle (fig. 173, A, m /«) is a long, slender, compressed, slightly bent bone, continued from the articular cavity at the end of the acromion to near the median line of the episternum, anterior to but parallel and in contact witli the branches of the epi- sternum, with which the clavicles finally co- alesce, but at an earlier period in the Orni- thorhynchus than in the Echidna. These clavicles are the homologues of the os fur- catorium in the bird : the T-shaped episternum (fig- 173, A, t~) is feebly represented in birds by the median process continued forwards be- tween the coracoid articular cavities from the fore part of the sternum. It is in Lizards, and especially in the extinct Ichthyosaur, that the episternum presents the same form, develop- ment, and relation to the clavicles, as in the Monotremes. The epicoracoids again are want- ing in the bird, but they are present in lizards, and the remarkable breadth of the coracoid in the Enaliosauria is due to their presence, al- though, singularly enough, they are anchylosed to the coracoids in these extinct reptiles, while in the warm-blooded Monotremes they remain separate. In the Echidna they are articulated with the coracoid by a true synovial joint. To render the resemblance between the Mono- treme and the Bird complete, in respect of the structure of the scapular arch, the episternum must be reduced to a short and simple process attached to the anterior part of the manubrium sterni, the epicoracoids must be removed, and the clavicles anchylosed together at their mesial extremities.* The humerus is a short and strong bone, exp
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