ANOMIAD At. 39 
Lamarck has made Pecten and Lima the types of the Pecti- 
nide, and Ostrea that of the Ostreade ; so far we concur; but 
we must remove Anomia from the Ostreade, with which, 
though it has the relations of the great subcentral muscle, 
and absence of tubes, still there are closer ones, of a different 
character, with the Palliobranchiata and the Pectinide. 
Though the characters of the great subcentral or posterior 
adductor muscle, the rudimentary, or no foot, and absence of 
siphons, are very decided ones, and common to this particular 
order or race, still it is not necessary that Anomia, Pecten, 
and Ostrea should on those accounts form a single family, any 
more than the Veneride, Mactride, and Cardiade, because 
they have distinct tubes, foot, and are strict Dimye ; therefore 
these reasons, and those under each particular head, have 
determined us to constitute Anomia, Pecten, and Ostrea as 
distinct families. 
Anomia then, with its single species, constitutes the family of 
the Anomiade, which we fix, according to our method, the first of 
the Lamellibranchiata, as it forms the decided point of passage 
from the Palhobranchiata, by its constant state of fixture, by 
a prolongation of the adductor muscle, through a perforation 
of the valve, to marine substances, either by a ligamentous 
or testaceous point of adherence; it also shows a similarity 
in the disposition of the ovarium on the mantle, and posi- 
tion of the animal in the shell. It will be observed that 
in this statement there is not a single point of community 
between Anomia and the Ostreade. Though Anomia, by the 
small byssiferous foot, and the very simgular doubled-up struc- 
ture of the branchial laminze, shows a very intimate connection 
with the Pectinide ; nevertheless, from its constant fixity, the 
perforated valve, ligamentous attachment, the texture of the 
shell, its proteiform shape, and the hinge, it cannot, without 
violence to established distinctions, be allocated with that 
group. I thmk I have adduced sufficient reasons to support 
the severance of Anomia from the Pectinide and Ostreade : 
and I consider that there are equally good reasons for the 
separation of Pecten and Ostrea, 
