No. 465.] STUDIES OF MYXINOIDS. 643 
position, the hagfish swims rapidly after, keeping in this way in 
constant touch with it. 
This tooth plate is worked by five muscles, three of which 
form a unique mechanism called by Dr. Ayers the “ club.” 
These muscles lie close to the ventral surface and may all be 
seen when the ventral skin and body musculature are deflected 
back. The two that do not belong to the “club,” lie ventro- 
cephalad of it (Fig. 3). The more lateral one arises as a narrow 
Fig. 3, Fig. 4. 


Fic. 3.— The “club muscle” and its accessories. Ventral view. 2. £., basal plate; c. m., 
circular muscle; Z. »r., long muscle; 7. m., perpendicular muscle. 4 natural size. 
Fic. 4.— The “ club muscle" and it ories. Lateral view. Half of the circular muscle 
has been cut away in order to show the long muscle. ¢. m., circular mu 
muscle ; 2. mz., perpendicular muscle; 7 ?., tooth plate. 4 natural size. 

scle; 2. m., long 
band of fibers along the lateral edge of the cephalic half of the 
caudal section of the basal plate, runs cephalad, then curves 
slightly mesad, joining its fellow of the opposite side in a com- 
mon aponeurosis, about a quarter of an inch behind the mouth 
opening. The aponeurosis continues forward until it reaches 
the mouth opening, where it fuses with the connective tissue 
which supports the mucous membrane of the lower lip; here it 
divides, each half deflecting posteriorly and laterally, to attach 
itself near the cephalic border of the tooth plate. The contrac- 
tion of this muscle helps the two halves of the tooth plate to 
close together. 
