218 PHOLADID A. 
adductor muscle of bivalves, which is here, as in Pholas, 
wanting, to the remarks on which we particularly refer. 
I close these observations by stating, that the masses of 
the foot, medial adductor, and posterior sphincter supply their 
respective parts of the body with the minor muscular threads. 
It is time to inquire about the nervous agencies that 
stimulate the action of these powerful muscular organs, and 
we find their volume, as in Pholas, to be apparently not in 
accordance with them. There are just above the mouth two 
minute gangla so nearly confluent that they may be con- 
sidered as one; from them, two very slender threads descend 
to the roof of the anal aperture, distributing numerous rami- 
fications to the proper stomach and foot, whilst the mai cords 
pass into the base of that portion of the tubular mantle which 
contains the liver, ovarium and pericardium, in a distinct 
independent membrane that may be called a peritoneum, and 
in their passage under these organs they furnish them with 
filaments, and then piercing the fundus of the peritoneum 
enter the pericardium, and form a junction with a second 
larger ganglion that is fixed in that cavity in some measure 
enveloped by the heart and auricles, and is only visible when 
the pericardium is cleared of them: this mass supplies the 
terminal part of the ovarium, the entire branchiz, and all the 
posterior parts of the body with nervous threads. 
The digestive organs next present themselves. Authors 
have said there are two distinct stomachs; this is not so: 
they have mistaken the peritoneal cavity containing the liver, 
ovarium and pericardium, for one: the true and only stomach 
is within the hemispherical valves, im immediate contact with 
the greenish-brown liver that pours the bile into it from above ; 
it is very small; the walls are simple; and the elastic stylet 
and gizzard, which some naturalists denominate the tricuspid 
membrane, work within it as a gizzard and attritor. 
I have carefully dissected the apparatus of the present 
species, and have it on a card in a united state, showing the 
hard horny parts of the rubbing portion. Some authors say 
that this machine is not to be found in all bivalves. Which are 
without it? Iam inclined to think that it is absent m none. 
