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52 A7/ierica?i Seashells
Identification of Chitons
It is essential for accurate identifications to refer to one or more ot the
ten technical terms used in describing the various parts of the chiton. A few
minutes' study of figure i8 will prepare the reader for the photographs,
identification drawings and descriptions of the species. Jumping to conclu-
sions from the photographs instead of ascertaining the family or genus first
will lead to discourag-ino- results.
ORRNuLes
EXTERIOR INTERIOR
f^NTeRioR vAt-ve
Rl^OlftLLY RtftftEO
nEDiftN vftLvea
LftTERRU M«E«
RftOlADiALuY NOOi^LOse
DlVftRlCAT|N& LINES
TU&UM
Pleural tract
central area
MUCRo
POSTtRiOA V(\LVE
Figure i8. Parts of the chiton shell.
INSERTION
pLAie TEETH
5VJTU8R1. Pl_flr£
All the chitons discussed in this book bear eight shelly valves which
cover the body of the creature and are bound together by a leathery girdle.
The chitons without valves (Aplacophora) are too rare to be conveniently
included here. A view of the underside of a living chiton will show the
rather small, separate head and its mouth and, behind this, the larger, ob-
long foot. On each side of the foot is a straight row of closely packed gills.
The head bears no tentacles or eyes, although the valves of many chitons
bear numerous shell eyes.
Each chiton possesses three types of valves: (i) the anterior valve at
the head end, (2) six intermediate valves, and (3) the posterior valve at
the hind end. The shape and ornamentation of these valves are used for
identification purposes, and for this reason the various areas of the valves
have been named. Removal of the last two valves by the soaking of dried