18l> ANODONTA — MUSCULAR SYSTEM. 
The Adductor iiiuscles are also considered to be a great local 
develoi)meiit of the pallial muscles, with which they are continuous ; 
in Amxlunta the adductors are formed by two large, powerful and snh- 
e([ual muscular masses, composed of numerous closely arranged 
muscle tihres and jjlaced at opposite ends of the body, at about an 
ecpial distance from the ligament ; they pass perpendicularly through 
the body of the mollusk between the inner faces of the valves which 
they unite together and close by their contractions, the anterior 
adductor being anterior and dorsal to the mouth, while the posterior 
lies beneath and anterior to the rectum, Imt they, in common with 
the extrinsic muscles generally, gradually move with the growth of 
the shell, diverging and becoming more distant from the hinge and 
from each other, leaving traces of their former i)ositions by the 
gradual narrowing and convergence towards the umhones of the 
scars, which mark their })laces of ])rior attachment. 
The Pedal mnscles are paired 
.symmetrically, and formed by the 
retractor, })rotractor, and levator 
or I’etentor muscles, which are all 
proximally attached to corres- 
ponding jmsitions on the inner 
surfaces of each valve, on which 
they leave di.stinct impressions or 
scars; distally they mainly ter- 
minate amidst the intrinsic mus- 
culature and tissues of the foot. 
'I’he Anterior protractors are 
111 u sc u lar masses formed by radiately 
divergent muscle tihres, which assist 
in the protrusion of the foot and 
are spread over and suiierticially 
attached to the surface of the foot 
and lU'oximally in.serted on each 
valve, a short distance from and 
posterior to the anterior adductor. 
'I'he Anterior letractors, at their origin, are often continuous 
postero-dorsally with the neighbouring adductor, they iienetrate 
deejily within the tissues of the foot, and for the most part are more 
deejily imbedded than the fibres from the ])osterior retractors ; they 
Kk;. — IVansvcrse section tlirougli 
niuerior region Anoiionta anatina showing 
tfie arrangement of the foot muscles anti ilie 
tluplicature of mantle (after Vogt and Vung). 
a. a. anterior aorta ; Iks. hlood sinus at base 
of palps; c.nt. cross muscles seen ns cut 
transversely ; c.t. connective tissue about 
digestive gland ; l.ti. ducts of liver or diges- 
tive gland ; l.ni. longitudinal pedal muscles ; 
/./. lalnal palps ; nr. muscles between foot 
and body ; p.a. pedal artery ; p.g. pedal 
ganglia ; r. rectum ; st. stomach ; t.ni. trans- 
verse pedal muscles. 
