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Show 1874.] MYOLOGY OF PHRYNOSOMA. 75 Rectus abdominis has the same attachments as in L. belli. Its anterior portion is extremely thin, and is covered by a connective tissue loaded with pigment-cells, which tissue also covers over the sacro-lumbalis. It is a singular fact that there is not the slightest trace of a trapezius in this lizard. Latissimus dorsi (figs. 2 & 3, L.D.) has an extraordinary arrangement in this subject. It arises from the spines of the third and fourth dorsal vertebrae, as a narrow muscular band which passes straight across the back, over the posterior end of the scapula, until it reaches the second dorsal rib, from which it takes a fresh and more extensive origin ; the external fibres of this part of the muscle arise more posteriorly, from the third, fourth, and fifth dorsal ribs. The whole passes forward and ends in a flat tendon, which is inserted as usual into the posterior surface of the humerus just behind the insertion of the teres minor. It sends off a' tendinous slip to join the inner head of the triceps - a n arrangement which occurs also in Iguana, according to Mr. Mivart*. That part of the muscle which is situated between the scapula and the vertebral column was so closely attached to the skin as to be with difficulty dissected from it. Levator scapula (fig. 3, L.S.) arises from all that portion of the suprascapula which is not occupied by the infraspinatus, with the exception of a small portion situated at the junction of the dorsal with the posterior border ; it passes forward to be inserted into the transverse process of the axis. Sterno-coracoidalis resembles in every respect the corresponding muscle of L. belli. Sterno-coracoidalis externus (fig. 2, See.) arises from the internal surface of the coracoid, close to its lower or articular edge, and a short distance from its anterior point, and passing backward is inserted into the outer angle of the sternum covered by the ligament of the triceps. There are three serrati (fig. 2, S.A. 1, S.A. 2, & S.P.) precisely resembling those of L. belli. Supraspinatus (fig. 1, S.S.) arises from the anterior margin of, and from the membrane covering the coracoid fenestra, and is inserted into the anterior and outer point of the humerus in front of and nearer the head of the bone than the infraspinatus. Infraspinatus (fig. 3, I.S.) arises from the central portion of the outer surface of the scapula and suprascapula, and from the anterior edge of that bone at the scapuloclavicular articulation ; it is inserted into the outer edge of the humerus, just beyond the insertion of the supraspinatus. Teres minor (fig. 3, Ts.M.) arises from the inner edge of the scapula at its point of junction with the coracoid ; it passes beneath the clavicle, and being, as usual, bound down by a tendon from the long head of the triceps, is inserted by muscular fibres into the humerus, commencing immediately within and just behind the anterior border of the insertion of the infraspinatus, and extending obliquely * P. Z. S. 1867, pp. 768, 780. |
