ANOMIA. 41 
position. This curious configuration of the branchiz is that 
of the Pectines, but not of the Ostree. 
At the anterior side, which is easily known by being oppo- 
site the conspicuous anal tube—or if the shell is placed on its 
front edge, with the perforated valve to the right hand of the 
observer, it will be farthest from him—is situate the oval 
margined mouth with its large aperture, which is very high 
towards the dorsal range, and has around it two plain linear 
membranes that are continuations of the branchize, which at 
this pomt have become slender. These laminz expand at 
each side the mouth into two pair of long delicate labia, fixed 
by the entire length of the longest sides, folding on each 
other; they are finely striated on both surfaces; the colour is 
light to dark brown. ‘The foot is almost reduced to nothing ; 
it is fixed to the body under the mouth, and is a small, yellow, 
obtuse, subeylindrical, pendulous, deeply-grooved organ, capable 
of spinning a byssus, which we have seen, and may serve to 
fix the animal in conjunction with the operculum. 
It is strange that nature should have furnished this animal 
with a foot and byssal groove of so small a size as apparently 
to be of little use, unless we suppose it to have the power of 
freeing itself from the bodies to which it is attached; and 
this idea is by no means without the verge of possibility. It 
is known that the Arce, Pectunculi, and other byssal bivalves, 
can detach themselves from their fixed position by abandon- 
ing the byssus. May not the dnomie dissever the end of the 
adductor muscle from the calcareous operculum? This in- 
ference arises from the presence of a byssal foot, which would 
then have a pro tempore use, whilst the animal in a change of 
locality is again fixing itself. These ideas are fortified by the 
statement of our dredger, who affirms that he is constantly 
hauling up pieces of rock studded only with opercula: this 
fact is certainly no proof that the animals detached them- 
selves, but it is a link im a chain which has a certain value. 
Nevertheless we are inclined to think the genus a fixed one 
for life. 
The ovarium is an extensive, inflated, sinuated lobe, origi- 
nating on each side the liver, coasting the body, and glued to 
