CLASSIFICATION 15 
There are eight plates or valves in all on the back of 
the animal, fitting one over the other like the tiles 
ona roof. Generally the lorica is surrounded by a 
leathery “ girdle,” so called, which helps to unite the 
several plates, and which, though sometimes naked, 
is usually studded with scales or beset with bristly 
spines. 
In some forms the body is very long, and the 
shelly plates are placed at intervals. The muscular 
foot extends the whole length of the under surface 
of the body; the end of the snout is just visible; 
there are no tentacles. A row of small gills is seen 
along each side under the edge of the mantle. The 
valves are perforated for the passage of sense organs, 
which in the family Chitonidz are in part converted 
into eyes. When detached from the rocks to which 
they cling, the animals will coil up after the fashion 
of the well-known Wood-Louse. 
Order II.: The APLACOPHORA, or SOLENOGASTRA, 
are so modified that they scarcely resemble molluscs 
at all. The body is worm-like, and there is no trace 
of a shell, but the much thickened outer skin con- 
tains shelly spicules. The foot is extremely reduced, 
or altogether wanting. The gills are in a chamber 
at the latter end of the body, into which chamber 
also the excretory orifices open. Their blood is red. 
Two sub-orders are distinguished : 
Sub-Oider 1: NEOMENIINA (Plate IX., Figs. 4 
and 5), in which the foot is sunk in a groove along the 
