ON MOLLUSCA. 279 
much to specialize or render rigorous their characters. But we 
must not deny that a considerable number of them ought to 
be, and have been, already adopted, and that he was the first 
to call the attention of conchologists to those extremely minute 
shells termed microscopic ; and that, although this part of his 
labour ought certainly to be considerably modified, conchology 
is not the less indebted to him for a real service. He has also 
separated from the multivalves the shells or teste of the ana- 
tifee, under the name of fissivalves. 
A few years afterwards, M. Megerle proposed a new distri- 
bution of shells, but none of it we believe has been published, 
except the part which treats of the bivalves, in the Berlin 
Magazine for 1811; and although he has entitled it a new 
system of conchology, it is evident that he follows Linneus 
almost scrupulously, with this difference, that he has esta- 
blished a tolerably great number of new genera, which have 
since been proposed and admitted by others. 
Finally, M. de Blainville (to whom, as we have already said, 
we are indebted for the principal part of this essay), in the 
Memoire read at the Philomathic Society, and inserted in its 
bulletin, although his classification referred essentially to the 
animals, and not simply to their envelopes, has introduced 
some new considerations into conchology, by shewing that the 
shell, especially in the univalves, is essentially the protecting 
body of the organs of respiration, of which it follows, to a cer- 
tain point, the general form and position. 
He has also called attention to the employment of a new 
character, drawn from the symmetry or non-symmetry of the 
univalve shells, in relation with the organs of respiration, and 
has replaced the oscabriones among the multivalves. 
We might very considerably lengthen this critical analysis 
of the works of authors who have written on conchology pro- 
perly socalled. Butit would be superfluous to speak of those 
who have added almost nothing to the art of classifying sheils, 
