456 MR. ST. GEORGE MIVART ON THE [June 24, 
The other part of the digastric (figs. 1, 2, & 3, D. 1) is larger, and 
springs from the dorsal end of the first branchial arch (above the 
attachment of the levator arcus primi), and is inserted behind the 
first part into the tendon before mentioned. 
Levatores arcuum* (figs. 1, 2, & 3, L. A, & L.A.1, also fig. 2, 
L.A.P). These are much developed, and the one going to the 
first branchial arch is remarkably distinct from the rest. This, the 
levator arcus primi (fig. 2, L.A.P), is quite hidden until the 
digastric is pulled outwards and the anterior part of the dorso- 
lateral muscular mass inwards towards the middle line. When 
this is done the levator arcus primi is to be seen passing out- 
wards and backwards from the exoccipital and opisthotic to the 
anterior margin of the first branchial arch, very near its superior 
extremity. 
The levatores* of the second and third branchial arches arise 
mainly from the dorsal fascia ; but the most anterior part (figs. 1 & 2, 
L. A. 1) seems to be differentiated off from the anterior end of the 
dorso-lateral muscular mass, and covers, and is similar in direction 
to, the hidden levator arcus primi. In the figure, between the most 
anterior part (fig. 1, L.A. 1) and the first part of the digastric 
(fig. 1, D. 1) a portion of the anterior end of the dorso-lateral mus- 
cular mass is seen to be interposed. 
Mylo-hyvideus anterior+ (figs. 4 & 5, M. H.1). This muscle is 
relatively smaller than is its homologue in Menopoma. It arises 
from the inside and lower border of the ramus of the mandible, and 
unites with its fellow of the opposite side without forming any di- 
stinct longitudinal tendinous interval. 
The mylo-hyoideus posterior} (figs. 3, 4, & 5, M. H. 2) is a con- 
siderable muscle, the postero-inferior part of which is enclosed on 
both sides by the skin forming a free fold or opercular flap beneath 
the throat. The muscle arises from the dorsal segments of the 
hyoidean cornu and first branchial arch, also from the fascia invest- 
ing externally the voluminous cerato-hyoideus externus. Passing 
downwards it unites with its fellow of the opposite side, a sort of 
linea alba marking their junction, At its anterior part this muscle 
is placed above the mylo-hyoideus anterior, the latter being super- 
ficial to it. 
I could find no trace of the muscle which I have described in 
Menopoma as the constrictor faucium. 
Constrictor pharyngis§. This consists of two parts: one (the 
dorso-trachealis) arises from the fascia external to the dorso-lateral 
muscular mass bebind and beneath the levatores arcuum; the 
other (the hyo-trachealis) springs from the postero-ventral surface 
of the third branchialarch. The fibres converge and join the fellow 
muscle of the opposite side beneath the trachea. 
The genio-hyoideus || (fig. 4, G. 1) is a rather long narrow muscle 
* Fischer, /.c. p. 81, tab. ii. B. da. + Fischer, J. c. p. 41. 
+. Fischer, /.c. p. 42. § Fischer, 7. c. p. 89. 
|| Fischer, 2. ¢. p. 55. 
