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CLASS III. 
Corticiferous Polypidoms , composed of two substances, 
one exterior and enveloping s called rind, or incrustation , 
the other named axe, placed at the centre , and support- 
mg the first . 
GENERA 
BELONGING TO THE FIRST ORDER OF THE THIRD CLASS. 
Polypi none, or not perceptible. 
Ephydatia. Fresh-water Polypidom, of a spongy 
nature ; colour green ; and in long masses, which are 
lobed or bundled together. 
Spongia. Polypidom of a porous mass, lobed, 
ramified, turbinated or tubulous ; formed of horny 
or leathery fibres, flexible, interwoven, or glutinated 
together, and surrounded or enveloped, in a living 
state, with a gelatinous, irritable, and very fugitive 
substance. 
GENERA 
BELONGING TO THE SECOND ORDER OF THE THIRD CLASS. 
The Polypidoms of this order are usually tree- 
formed and inarticulated ; the interior consisting of 
an axe, in general horny and flexible, sometimes 
sufficiently hard to receive a fine polish, at others 
