24 Marine Shells of the Western Coast of Florida 



The characteristic specific features and the intrinsic beauty of 

 shells are best exhibited in well-prepared specimens, but every col- 

 lection should include a few shells of each species in the undisturbed 

 natural condition, with epidermis intact and incrustations and barn- 

 acles unremoved.* 



Some definite plan of classification should be adopted for the 

 cabinet, and each group of specimens should be clearly labelled with 

 the name, the date, and the locality in which they were collected. 



SYSTEMATIC DESCRIPTIONS 



Class AMPHINETJRA 



The foundation of this distinct class of the Mollusca is the com- 

 plete bilateral symmetry of its members. The name Amphineura 

 (from the Greek combining form, amphi, both, in both sides; and 

 neuron, nerve) refers to the balanced arrangement of the nervous 

 system. The two orders of this class, the Aplacophora — not bear- 

 ing plates — and the Polyplacophora — bearing many plates, are based 

 upon the absence or the presence of a shell, and the naked mollusks 

 of the first order are the simplest and most lowly organized mem- 

 bers of the phylum Mollusca. 



The Polyplacophora or chitons have a multivalve shell which 

 covers and protects only the dorsum of the animal's flattened and 

 elongated body. The unprotected ventral surface is equipped with 

 a broad, suckerlike muscular foot, admirably adapted for creep- 

 ing and for adhering tightly to the firm surfaces of rocks, shells, 

 and corals over which most chitons browse in search of their vege- 

 table food of algae and diatoms. Chitons are native to all seas, usually 

 at moderate depths. They are sluggish creatures, generally noc- 

 turnal in habit and appear to avoid light by hiding during the day- 

 time in crevices, dead shells, and under rocks. Some are said to re- 



* The scientifical collectors, or naturalists, are always desirous of having 

 the shells in their rough state, or just as they are fished. This method, though 

 extremely useful, is not to be absolutely followed; not only because their 

 beauties would be lost, but also on account that the different species could never 

 be truly defined. However, as a medium, I would advise all collectors to have 

 some shells of each genus in their rough state, while the others should display 

 their beauties by all the accomplishments of art. — Emanuel Mendes da Costa, 

 1776. 



