32 
crimes is placed in this group by some of the later writers, but 
it has nearer relations with the true Crinoidea. 
Fig. 23.—CYSTOIDS. 
a b o 
This group, the Stone-lilies, embraces the most beautiful and 
attractive forms of organic remains known. They are sack-like 
bodies, made up of separate plates arranged in rays from the base 
of the body, and are surmounted by a series of arms and fingers, 
also composed of a large number of pieces. The whole is sup- 
ported on a stem, composed of plates of greater or less length, 
and was rooted to the bottom of the ocean, or to other substances, 
like a plant. From this, and the similarity of the body and arms to 
parts of a flower, they have been called Slone-lilies. Although 
rooted and fixed and so plant-like in appearance, they were true 
animals and had animal functions. The cavity of the body con- 
tains a calcareous convolute plate, which is supposed to have sup- 
ported the stomach or digestive organ and is frequently found 
preserved in the fossil forms. Crinoids were extremely abundant 
in the Palaeozoic seas, and vast beds of limestone are made up 
principally of their remains. Their remains are found from the 
earliest period of fossils (Potsdam) to the present, when but few 
forms are known, one of which is represented in Case n, Sect. 6. 
As fossils they are usually found only in a fragmentary condition, 
as, in consequence of being made up of a large number of pieces, 
