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Show 458 MR. ST. GEORGE MIVART ON THE [June 24, backwards, it is inserted into the outside of the dorsal part of the first branchial arch, immediately beneath the insertion of the second jtart of the digastric. Fig. 5. OS. Deepest muscles of left side of ventral surface of head, the cerato-hyoideus externus being drawn strongly forwards. C.A.I, C.A.2,& C.A.3. Constrictores arcuum. CHE. Cerato-hyoideus externus. C H I. Cerato-hyoideus internus. M.H.I& M. H. 2. Mylo-hyoideus. S. H. Sterno-hyoid. Cerato-hyoideus internus* (fig. 5, C. H. I). A very much smaller muscle than the last, and, as Fischer says, "spindle-shaped and tendinous at each end." It arises from the inner end of the posterior surface of the hyoidean cornu, and is inserted into the lower end of the dorsal segment of the first branchial arch. Constrictores arcuumf (fig. 5, C. A.\, C. A. 2, and C. A. 3). There are three of these small muscles. The first connects tbe ventral end of the second branchial arch with the dorsal end of the ventral segment of the first branchial arch. The second and largest of the three connects together the ventral ends of the dorsal segments of the first and third branchial arches. The third muscle connects together the ventral ends of the dorsal segments of the second and third branchial arches. A muscle"]" (figs. 4 & 5, S. H), which corresponds to the sternohyoideus of Menopoma, though here there is no sternum, and is in fact the anterior continuation of the rectus, passes forwards and is inserted into the dorsal surface of the urohyal and into the ventral surface of the ventral segment of each first branchial arch, near its junction with the basihyal. * Fischer, /. c. p. 72, tab. i. fig. 4, pa. t Fischer, /. o. p. 74, tab. i. fig. 3. ca and ca'. J Fischer. I.e. p. 104. |