ECHINIDA, 281 
sented here, supported and protected by a very complicated frame- 
work, which has received the name of Aristotle’s Lantern (Fig. 115). 
Fig. 114 represents Echinus lividus, 
with all its spines removed; the 
other shows the masticatory organs, 
that is to say, Aristotle’s Lantern. 
To give the reader another idea of 
the buccal organ in the sea-urchins 
let him glance at a flattened form 
from the southern seas, Clypeaster 
rosaceus, represented in Figs, 116 and 
117, an outline of the entire animal. 
The shape of Clypeaster rosaceus 
is oval, straighter in front, and thick pig. 514. —Buccal armature of Echinus 
and rounded at the edges. It is lividus. 
more common and more largely dis- 
tributed than perhaps any other allied species, and it is supplied 
with four or six rows of ambulacral feet. 
It is not easy to understand why the dental framework of the 
Fig. 115.—Masticating apparatus of Echinus lividus. 
sea-urchin has been called Aristotle’s Lantern, for this formidable 
apparatus resembles the front view of a battery of cannon more than 
a lantern. It consists of a series of pieces designated by the names 
of compass, scythe, pyramid, and plumula, which it would serve no 
useful purpose to describe in detail here. 
We have said that the mouth of the sea-urchin is quite out of 
