THE NEW-YORK FAUNA. 
DIVISION If. INVERTEBRATED ANIMALS. 
CLASS VI. MOLLUSCA. 
ANIMALS OF A SOFT OR GELATINOUS STRUCTURE, NOT COMPLETELY SYMMETRICAL; WITHOUT 
ANY SOLID SKELETON OR VERTEBRAL CANAL, OR ARTICULATED LIMBS. ALMOST ALWAYS 
FURNISHED WITH A DEVELOPMENT OF THE SKIN, WHICH ASSUMES A MORE OR LESS HARD 
CONSISTENCE, UNDER WHICH THE ANIMAL CAN CONCEAL ITSELF. SOME HAVE A SOLID CAL- 
CAREOUS COVERING OF ONE OR MANY PIECES, WHICH ARE TERMED “ SHELLS.” CIRCULATION 
DOUBLE, THAT IS TO SAY, THE PULMONARY CIRCULATION DISTINCT AND COMPLETE ; THE 
BLOOD WHITE OR BLUISH. BREATHE IN AIR OR WATER. OVIPAROUS AND VIVIPAROUS, CAR- 
NIVOROUS AND HERBIVOROUS. LIVING ON LAND, OR IN SALT AND FRESH WATER. 
Ozs. This class, in its now extended form, comprises all those animals of a soft or gela- 
tinous structure, with the above mentioned characters, found on land or in the water, and 
which are known under the popular names of Slugs, Cuttlefish, Sea-slugs, and Shellfish. 
These latter, which form a very large proportion of the whole class, are commonly called 
Shells, from their hard calcareous coverings. The arrangement of these varied and often 
beautifully colored shells constitutes the science of Conchology ; which, it will be perceived, 
is only a partial and incomplete view of the subject, unless accompanied with a study of the 
structure of the animals themselves. Various systems of arrangement have been proposed, 
each of which have some peculiar advantage ; but none appears preferable, in its outline and 
philosophical spirit, to that proposed by Cuvirr. We have therefore adopted it, with a few 
modifications from more recent writers. 
Fauna — Part 6. 1 
