38 ANOMIAD AE, 
ACEPHALA LAMELLIBRANCHIATA. 
ANOMIADA. 
The only genus of this family, Anomza, is one of the Ostra- 
cee of Lamarck’s monomyal order, which cannot be main- 
tained in its integrity; zoologists have long removed the 
Mytilide from it to the Dimye. It will be as well at once 
to state, that all the monomyal animals of that emiment 
naturalist are really Dimye. It will probably create some 
surprise when we say, that the only true Monomye are the 
Pholades and Teredines, as, we think, we have satisfactorily 
demonstrated in their respective anatomies. All other bivalve 
genera have two adductors; the anterior one im Anomia, 
Pecten, and Ostrea is of so small a volume, as almost to have 
escaped notice; and the great subcentral muscle in those 
genera appears of a size as if the two ordmary dimyal ones 
were amalgamated ; still the anterior adductor exists, and if 
carefully searched for will be found under the beaks, pomted 
out either by a single minute cicatrix, or by a little group of 
five or six closely united, very small, muscular scars; this dis- 
position of the cicatrices varies in all the genera, so does the 
main subcentral mass, as to shape and size. Careful dissec- 
tions of the animals will show the muscular filaments adhermg 
to the circumscribed area under the beaks; but im oyster- 
shells that have been exposed to the action of the sun and air, 
and vicissitudes of weather, the minute anterior adductor is 
perfectly visible. In the three genera we have mentioned, 
these muscles are of small size; they, however, in the next 
family, the Mytilide, though still small, have become more 
developed, and in the following one of the Arcade they have 
completely acquired the typical size and position, which is 
maintaied in all the remaining families, until they reach the 
Pholadide, when they merge into a single medial adductor, 
both in the Pholades and Teredines. 
