No. 3.] MUSCLES AND NERVES [IN AMIA CALVA. 73! 
Above the vagus, the first intermuscular septum, follows the 
postero-lateral edge of the skull to its upper surface, and then 
runs medianward along the hind edge of the squamosal and 
parietal under the extrascapular. There it is somewhat broken, 
so that two or three parts of it appear as short ligaments, vary- 
ing slightly in every specimen. Below the line of its attachment 
to the dorsal edge of the skull it is pushed forward into the 
temporal groove, crowding out the first muscle segment, so 
that it is the anterior surface of this part of the first septum 
that forms the upper surface of the muscle mass that fills that 
groove. In the first septum there are thus two pockets, a median 
one directed backward, as in the other septa, and a lateral one 
directed forward into the temporal groove. Similar but much 
less marked lateral pockets are found in the second, third, and 
following septa. The second septum, and even the third, may 
acquire, with the corresponding muscle segments, an insertion 
in the temporal groove. 
Into the posterior pocket of the first septum, from the hind 
edge of the parietal, a strong, flat, ligamentous structure ex- 
tends, and ends free without insertion of any kind. From its 
dorsal and ventral surfaces muscle fibres arise, and have their 
insertions on the adjoining surfaces of the pocket. They 
represent all that can be found of that part of the first muscle 
segment that lies above the vagus. Below the vagus the first 
muscle segment is represented by a small pocket of muscle fibres 
found at the anterior end of the trunk muscles. Ventral and 
median to this point the edge of the trunk muscle runs _ back- 
ward and inward, and opposite the hind end of the basioccipital 
almost reaches the ventral cartilaginous processes of that 
bone (Fig. 63, Pl. XX XVII). At this point the trunk muscles 
cover ventrally the lateral occipital ligaments. The edge of 
the muscle mass then turns outward and backward, but the 
mass still covers ventrally the lateral ligament on the first ver- 
tebra and the lateral process and proximal end of the rib on 
the second. The lateral process and rib on the third vertebra 
are left fully exposed. One rib and three rib-like ligaments 
thus lie imbedded at their proximal ends in the upper end of 
the ventral portion of the trunk muscles. 
