ANOMIA. 41 



position. This curious configuration of the branchiae is that 

 of the Pectines, but not of the Ostrea. 



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 branchiae, which at 

 this point have become slender. These laminae 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, subcylindrical, 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 Area, Pectunculi, and other byssal bivalves, 

 can detach themselves from their fixed position by abandon- 

 ing the byssus. May not the Anomus 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 &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 in 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 



