PREFACE TO THE FIRST EDITION. XXI 
forms of shells belong, and to arrange the latter from that con- 
siderations; but as to the ulterior divisions of those shells whose 
animals resemble each other, I have examined them only so 
. far as to enable me to describe those admitted by Messrs de 
Lamarck and de Montfort; even the small number of genera or 
subgenera which are properly mine, are derived from observa- 
tions on the animals. Inciting examples I have confined my- 
self to a certain number of the species of Martini, Chemnitz, 
Lister, and that only (the volume of M. de Lamarck, which 
is to contain these matters, not being published), because I 
was compelled to fix the attention of the reader on specific 
objects. In the selection and determining of these species 
however I lay no claim to the same critical accuracy I have 
employed for the Vertebrated animals and the naked Mol- 
lusca. 
The excellent observations of Messrs Savigny, Lesueur, 
and Desmarest on the compound Ascidia, approximate the 
latter family of the Mollusca to certain orders of Zoophytes— 
a curious relation, and an additional proof of the impractica- 
bility of arranging animals on one single line. 
The Annulata. (the establishing of which order, although 
not the name, belongs de facto to me) have I think been ex- 
tricated from the confusion in which they had hitherto been 
involved among the Mollusca, the Testacea, and the Zoophy- 
tes, and placed in their natural order—even their genera have 
been elucidated only by my observations on them, published 
in the ‘¢ Dictionnaire des Sciences Naturelles,”’ and elsewhere. 
I can say nothing relative to the three classes contained in 
the third volume. M. Latreille, who, with the exception of 
some anatomical details, founded on my own observations and 
- those of M. Randohr, added to his ee is its sole author, 
will spare me that trouble. 
As to the Zoophytes, which terminate the animal kingdom, 
I have availed myself, for the Echinodermata, of the late work 
of M. de Lamarck, and for the Intestinal Worms, of that of 
M. Rudolphi, entitled Zntozoa; but I have anatomized all 
the genera, some of which have been determined by me only. 
