184 PHOLADID#. 
posterior end united to the intestine, and attached by the 
middle to the hyaline stylet. 
This singular organ, so well known to exist, I believe, in all 
bivalves, has caused some difference of opinion as to its use ; 
but I think when all the incidents attached to it have been 
mentioned, they, m conjunction with the position in the 
stomach of the tricuspid organ, can lead to no other conclu- 
sion than that the apparatus is a gizzard worked by the foot 
and elastic stylet to comminute the food, and is analogous to 
the gizzard in many of the Gasteropoda. The stylet is for the 
basal half cylindrical, and tapers from thence to the stomach, 
where it makes a loop, and is fixed by a filamentary muscle to 
the gizzard or tricuspid membrane ; its colour is hyaline milk- 
white, and in certain lights reflects the metallic hues; the 
working point of support is the centre of the basal part of the 
foot, through the pedicle of which it proceeds obliquely to the 
stomach, guarded by a sheath which appears to secrete a 
lubricating fluid, probably having its source from the liver, 
through the centre of which it passes to its junction with the 
corneous attritor; it is eminently elastic, formed of a suite of 
circular lines; it is impervious. I have submitted it to every 
sectional form, but the only departure from homogeneity are 
the fine circular elastic fibres ; in the species we now describe 
it is fixed by a short muscle to the bottom of the foot ; in 
P. parva it appears to rest, free. At one time I thought the 
stylet might be the vehicle of a solvent fluid from the stomach, 
but its impermeability negatives this idea; and if there is a 
connection with the foot from the stomach, it must be by the 
sides of the walls of its sheath ; in that case a solvent would 
neutralize the lubricity so necessary to its action, as a spring 
for the gizzard; besides, the most careful examination of the 
external and internal surfaces of the foot shows no connection 
between them, or orifice for the issue of a solvent. No ad- 
juvant powers of sight have enabled me, in this species, to 
discover the pore which is said to admit water to the foot of 
many of the bivalves, or to expel it if received from the 
stomach. 
{ now return to the intestine, which we left united to the 
