Non3.| “OSCLES AND NERVES TN: AMIA CALVA. SS 
forward a little, and are inserted along the front edge of the 
median, dorsal process of the metapterygoid, and on the upper 
surface of the bone in front of that process. The fibres of the 
outer portion of the muscle immediately behind this anterior 
part arise partly from the postorbital process, but mostly from 
the outer surface of the median aponeurosis of the muscle. 
The inner portion of the muscle begins about on a level 
with the front edge of the metapterygoid process; it arises 
entirely from the inner surface of the median aponeurosis 
which, in front of this point, has been merely a strong mem- 
brane lining the inner surface of the outer portion of the 
muscle. Its fibres arise at a considerable angle to the aponeu- 
rosis, curving inward and downward and then a little outward, 
thus forming a strong belly on the inner side of the muscle. 
The muscle has its insertion on the entire inner surface of the 
median process of metapterygoid, on the entire inner surface 
of the strong metapterygoid membrane, and on the outer 
surface of that small portion of the hyomandibular that les 
internal to that membrane, and is marked off from the rest 
of the bone by the line of attachment of the membrane to it. 
This small portion of the hyomandibular is much thinner than 
the rest of the bone and lies depressed below the level of the 
rest of its outer surface. It extends from the front, upper 
corner of the bone down along its front edge to the point 
where the metapterygoid joins or overlaps it, at about two 
thirds its length. 
dad. Dilatator Operculi. 
The dilatator operculi (Do, Figs. 30, 31, and 36, Pls. XXVI, 
XXVII, and XXIX) is described by McMurrich as a part of 
the first division of the levator arcus palatini, his description 
of it being: “Those [fibres] lying most posteriorly are directed 
backwards, passing under the upper extremity of the preoper- 
culum, thus fulfilling the function of the separate dilatator 
operculi of the Teleostei.” 
In all the adult and larval specimens that I have examined, 
without exception, the dilatator has invariably been found as a 
