1869. | THE MYOLOGY OF MENOPOMA, 261 
Fig. 3, 
Superficial muscles of right side. 
A, A. Adductor arcuum. JB. Biceps. C.A. Constrictor arcuum. C.F. Con- 
strictor faucium. D. Deltoid. D.1. Digastrie. £. Z. Extensor longus. 
Ex. O. External oblique. L.A. Levator arcuum. JL. D. Latissimus dorsi. 
M. Masseter. M.H.1. Mylo-hyoideus anterior. MM. H.2. Mylo-hyoideus 
posterior. _S. Subclavius, S.Z, Supinator longus. TZ. Trapezius. 7. 
Triceps. U, Ulnaris. 
Masseter (figs. 1, 3, & 5, M). This is an exceedingly thick 
muscle, which arises from the anterior surface of the suspensorium 
as far as the margin of the parietal. It is inserted into the upper 
border and outer surface of the posterior part of the mandible. It 
covers externally the descending terminal portion of the temporal, 
which runs down in a sort of groove on its inner surface. 
The digastric (figs. 1, 3, & 5, D.1 & D.2) is a very large and 
powerful muscle, consisting of two parts, which are together inserted 
into the posterior extremity of the mandible. The hinder portion of 
the muscle arises from the dorsal fascia, closely connected with the 
similarly arising part of the posterior mylo-hyoid, and overlapping 
the levator areuum. The anterior portion takes origin from the 
occiput, the hinder surface of the suspensorium. Both portions 
pass over the cornu of the hyoid (without being directly connected 
with it) to their before-mentioned insertion. 
Levator arcuum (figs. 1 & 3, L.A). This is a small delicate 
layer of fibres springing from the dorsal fascia in the angle between 
the digastric and the temporal. Passing obliquely downwards and 
backwards, and covered, more or less, by the hinder part of the 
digastric and the posterior mylo-hyoid, the fibres go to the dorsal 
segments of the last three branchial arches as Fischer has described *, 
Mylo-hyoideus anterior (figs. 2 & 3, M.H.1). This forms, with 
* L.c. p. 83, tab. 4. fig. 2, Za. 
Proc. Zoou. Soc.—1869, No. XVIII. 
