SYSTEM OF
LINNÆUS.
"As you both assure me," said Mr. Elliot, "that you do not fail to make yourselves familiar with the nomenclature, or terms, used in conchology, I shall proceed this morning to the arrangement of Linnæus.
"This system is established upon the outward appearances, or external characters, of the covering bestowed by nature upon the animal, not upon the form of the animal itself.
"The three principal divisions you are already acquainted with, namely, Multivalves, shells composed of several parts called valves; Bivalves, formed of two parts; and Univalves, composed of one part or piece only.
"These divisions contain several genera, and the genera usually include many individual shells, but occasionally only one.
"The characters of every genus are permanent, and are therefore to be observed in every one of the species contained in the genus.
"Species are determined by shape, colours, or appearances on the surface of the shell: there are sometimes many varieties of the same species.
LINNÆAN
GENERA.