. The Australian zoologist. Zoology; Zoology; Zoology. ANDERSON. 109 of the ascending ramus (PI. svi., figs. 1, 2, text-fig. 1). Contraction of this anterior bundle on the left side, say, pulls the left ramus forward, and at the same time rotates its anterior end outwards. The right ramus, on account of. Fig. 1. Macropus giganteus, No. M. 3914. Dissection by R. Rawle, showing the internal pterygoid muscle; on the right the dissection is viewed partly from above. Drawn by G. S. Lightoller from photographs shown in PL xvi. the looseness of the symphysis, would lag behind slightly and thus the lo
. The Australian zoologist. Zoology; Zoology; Zoology. ANDERSON. 109 of the ascending ramus (PI. svi., figs. 1, 2, text-fig. 1). Contraction of this anterior bundle on the left side, say, pulls the left ramus forward, and at the same time rotates its anterior end outwards. The right ramus, on account of. Fig. 1. Macropus giganteus, No. M. 3914. Dissection by R. Rawle, showing the internal pterygoid muscle; on the right the dissection is viewed partly from above. Drawn by G. S. Lightoller from photographs shown in PL xvi. the looseness of the symphysis, would lag behind slightly and thus the lower in- cisors would diverge. The external pterygoid is much smaller than the internal, and runs backward almost horizontally to be inserted on the anterior border of the condyle and the articular meniscus, which is quite well developed at least in younger animals. Contraction of the external pterygoid would assist in drawing the ramus forward and to a slight extent in its rotation. Simultaneous contrac- tion of the right and left anterior bundles of the internal pterygoid would cause a wider separation without rotation. The main portion of the muscle runs in a more vertical direction and its contraction simultaneously with that of the mas- seter and temporal closes the mouth and brings the lower incisors together again, the lower molars at the same time gliding inwards on the upper molars as the two rami are brought nearer to the middle line. The outer fibres of the masseter (ro. m-asseter lateralis) may possibly, as suggested by Tullberg and Lb'nnberg, have some effect in twisting the lower edge of the mandible outwards, but it is more probable that they act as antagonist to the inward twist imparted by the internal pterygoid and steady the jaw. Dr. Lightoller has kindly supplied me with some interesting details regard- ing the masticatory and facial musculature of macropods, and a note on m. transversus mandibulae in the paca (Coelogenys paca). He finds by dissection of Macr
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