INTRODUCTION. 
Hiruerto the students of that group of animals named 
Mollusca, and all those British naturalists who have written 
on the subject (Lister excepted), have confined their atten- 
tion merely to describing the shelly coverings, shellsand teste 
of the testaceous Mollusca, without paying the least atten- 
tion to the animals themselves. The parts of the shell are 
named by them with terms not at all applicable to the 
parts of the animals they are destined to protect. The 
animals of the Bivalves are named Ascidiz by the same 
authors. 
It is to the writings of Poli, Cuyier, Savigny, De La- 
marck, Tilesius, Le Sueur, Meckel, Fischer, Say, Rafinesque 
and De Blainville, that we are indebted for those enlightened 
views which have been universally adopted by all those 
who feel and acknowledge that an accurate knowledge of 
their anatomical structure and their economy is essential 
in approaching towards constituting a natural system, and 
is alone neglected by those few who are bigoted to the 
artificial system of the immortal Linnzus. 
Without entering into any discussions as to the compa- 
rative merit of the various systems which have been pro- 
posed, I shall merely subject to my readers what are my 
