No. 3.] WUSCLES AND NERVES IN AMIA CALVA. 567 
pying a little more than one third of the inner surface of the 
bone. 
The levator has its insertion posterior to that of the adductor, 
and is double at its origin, arising behind directly from the under 
surface of the suprascapular, and in front by tendinous attach- 
ment to a tendinous formation, which extends backward under 
the extrascapular, from the hind edges of the squamosal and 
parietal. A part of the tendon of the muscle can usually be 
traced through the tendinous formation to the under surface of 
the parietal, near its hind edge, and at about the middle line of 
the temporal groove. This long and slender part of the ten- 
don lies immediately above the anterior extension of the trunk 
muscles that fills the temporal groove. 
The adductor lies anterior to the levator. Its superficial fibres 
form a thin, narrow band, which crosses the hindermost fibres of 
the adductor hyomandibularis at a considerable angle to them, 
lying on their upper, outer surface, and arising, just above their 
origin, from the lateral wall of the skull, the surfaces of origin 
of the two muscles being continuous. The deeper fibres arise, 
partly by numerous delicate tendons, partly by direct attach- 
ment, from the posterior process of the intercalar, from the 
postero-lateral angle or edge of the cranium immediately above 
that process, and from the hindermost lateral extremity of the 
squamosal, this last attachment not being an important one. 
The muscle in its deeper part is continuous at its insertion 
with the levator operculi behind, and with the adductor hyo- 
mandibularis in front. 
4. Review and Comparison of Muscles of Group II. 
The muscles described under this group belong to the hyoid 
and mandibular arches, or perhaps also, in part, to one or more 
preoral arches (No. 124, p. 448). They form a large, compli- 
cated, and very variable group, and their definite innervation 
is but little known. Any attempt to compare the muscles in 
Amia with those described in other fishes can, therefore, be of 
but little value in so far as the possible homologies established 
for the several muscles or the different parts of those muscles 
