566 ALELS. (VoL. XII. 
dorsal surface of the rays, unite with one or more of the cords 
encountered there. Some of these cords, alternately muscular 
and tendinous, extend as far upward and backward as the inner 
surface of the interoperculum; and other small, thread-like 
cords, found in the integument beyond the free edges of the 
rays, can be traced nearly, if not quite, to the upper edge of the 
operculum. In young fishes the fibres of the hyohyoideus 
extended up into the region of the levator operculi, but the 
continuity of the fibres, and hence of the two muscles, could 
not be established. 
3. Sub-Group 3. Muscles innervated by the Facialis alone. 
a. Adductor Hyomandibularis. 
This muscle (Az, Figs. 25 and 37, Pls. XXV and XXIX) is 
broad and short, extending from the auditory region of the lat- 
eral wall of the skull to the inner surface of the hyomandibular. 
Its line of origin begins on the petrosal, at the hind margin of 
the facial foramen, and extends backward and upward across 
that bone, and across the intercalar, nearly to the end of its 
posterior process. It is inserted on the inner surface of the 
hyomandibular, the line of insertion extending from the front 
edge of the bone, backward and upward, nearly to the hind end 
of the opercular process. It lies mostly below the internal 
opening of the facial canal, through the hyomandibular, but 
overlaps that opening somewhat, so that the facial nerve, in 
its passage from its cranial foramen to the internal opening of 
the canal, lies partly imbedded in the fibres of the muscle. 
The muscle runs outward, backward, and downward, lying, in 
its anterior portion, more nearly horizontal, and being there 
much shorter than in its posterior part. 
b. Adductor Operculi and Levator Operculi. 
These two muscles (Ao and Lo, Figs. 20-30, Pls. XXIII- 
X XVI) are continuous at their insertion, which is on the upper 
portion of the inner surface of the operculum, behind the artic- 
ulation with the hyomandibular, the surface of insertion occu- 
