644 THE AMERICAN NATURALIST. [VoL. XXXIX. 
This mandibular muscle (Figs. 3, 4), is called by Fürbringer, 
m. copulo-glossus superficialis, and by Müller, * der oberfläch- 
licher Vorzieher der Zunge.’ Both of these names are now 
inadmissible, as we are dealing with the lower jaw and not with 
the tongue as these authors thought. 
Mesad of this superficially placed mandibular muscle lies 
Fürbringer's m. copulo-glossus profundis, Müllers “tiefer 
Vorzieher der Zunge." This muscle (Figs. 3, 4), consists of a 
lateral and a mesial division which join together at the cephalic 
end. The lateral division arises from the lateral edge of the 
caudal end of the third section of the basal plate. Its fibers 
run laterally, then curving, run cephalad along the border of the 
mandibular muscle last mentioned. The mesial division also 
arises from the lateral edge of the third section of the basal 
plate, between the points of origin of the lateral division of this 
muscle and the superficial mandibular muscle. It runs forward 
between the lateral division and its fellow of the opposite side, 
being separated from the latter merely at its hind end. The 
combined mesial and lateral divisions of each side fuse together 
at the cephalic end into a common tendon for the two muscles. 
This tendon runs cephalad between the basal plate and the 
aponeurosis of the superficial muscle, turns dorsad at the cephalic 
end of the latter, and runs caudad to the tooth plate where KC 
divides again and is inserted midway in the length of the latter, 
close to the median line. This muscle, by contraction, draws 
the tooth plate forward, and by contracting to its full extent 
pulls it out of the mouth and into the vertical position. 
The other three muscles that manipulate the tooth plate form 
a structure aptly named by Dr. Ayers the “club muscle." This 
“club” is between three and four inches long and consists of 
a hollow circular muscle, a long muscle, and a perpendicular 
muscle. 
Of these three, the long muscle (Fürbringer's m. longitudinalis 
linguæ, Müller’s “innere Längsmuskel der Zunge”) is the only 
one zb direct connection with the tooth plate. This long muscle 
(Figs. 3, 4, Z. m.), is about three inches long, and from half to 
three quarters of an inch across its caudal end, tapering at its 
cephalic end to two tendons, one of which lies enclosed within 
