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Show 1890.] HELODERMA SUSPECTUM. 163 from these points. Passing downwards and forwards it becomes inserted by a strong tendon into the proximal third of the corresponding humerus upon its ulnar aspect. The outer margin of this muscle develops a strong tendon, which, as the muscle itself passes between the heads of the triceps to its insertion, branches off to insert itself into the triceps, upon its inner head. Mivart found a similar tendon to this in Lguana, and Sanders in Phrynosoma; but the latter anatomist found it absent in Liolepis. 18. Levator scapulae.-This is a flat, triangular muscle that arises fleshy from the external aspect of the anterior part of the scapular and suprascapular, and from the anterior margins of both of these bones. Its fibres converging as they pass directly forwards and passing between the deep muscles at the side of the neck, it is finally inserted by a strong tendon into the side of the atlas. 19. Pectoralis.-Heloderma has this important breast-muscle well developed ; it arises from the external longitudinal half of the entire length of the interclavicle, from the posterior border of the inner end of the clavicle, from the ventral aspect of tbe sternum, from the corresponding surfaces of the last four costal ribs and the intercostal fascia, and finally posterior to these parts from the fascia of those muscles of the abdomen which are situated deep to the pectoralis. From these several points of origin, a pectoralis of either side has its fibres converging to a point represented by the tuberosity of the humerus of the same side, and here they are inserted, tendinous, upon a line defining its mesial aspect, and for its entire margin. 20. Deltoicleus in the species before us arises by two heads-the anterior head from the underside of the mesial extremity of the clavicle ; the posterior head from the interclavicle close to the anterior head, and from the surface of the sternum immediately adjacent : these two heads are in contact for their entire lengths, and their fibres are sent directly to the corresponding humerus; passing backwards and outwards, they become inserted by a strong tendon upon the head of that bone, just anterior to the next-to-be-described muscle. It appears that Sanders found in Liolepis and in Phrynosoma only that part of the deltoideus which represents its clavicular portion present. I believe it has a double head in the Lguana. 21. The Supraspinatus is a flat, triangular muscle of the chest, which, in this lizard, arises from the anterior half of the mesial margin of the coracoid, by means of a strong aponeurosis ; the fibres converge as they take their way to the humerus of the same side, and are inserted, tendinous, into the tuberosity of that bone, close to the insertion of the pectoralis. Here in Heloderma the supraspinatus appears almost to be divisible into two parts, the anterior half of the muscle being connected with the posterior half by an easily separable fascia ; but as their origins are continuous, as well as their insertions, the muscle could in no way be properly described as having two heads. Hoffmann, who calls this muscle the m. supracoracoideus, informs us in his synonymy that it is the subclavius of Rolleston, the |