280 
CHAPTER VIII. 
FOSSIL STELLERIDE ; COMPRISING THE CRINOIDEA OR LILY-LIKE 
ANIMALS; AND THE ASTERIAD#, OR STARFISHES. 
Tue Raprata, or radiated animals, so designated because the 
parts of which the body is composed are arranged around a 
common centre or axis, are divided into three sub-classes ; 
namely, 1, the Polypifera, whose fossil remains were treated 
of in the previous chapter ; 2. the Acalepha, or Jelly-fishes, 
whose structures are so perishable as to render it improbable 
that any vestiges of them will be found in a fossil state, 
though imprints of the general outline of certain kinds may 
possibly occur ;* and, 3, the Hchinodermata, comprehend- 
ing under that term the Stelleride, or Crinoids and Star- 
fishes, and the Hchinoderms, properly so called. This sub- 
class is the subject of the present section ; it comprises four 
orders, viz. 
Crrinorpea, or Lily-like Animals. 
ASTERIADA, or Star-fishes. 
Ecuinip&, or Sea-urchins. 
HOLOTHURIADA, or Sea-slugs. 
Vestiges of the Stellerida are among the earliest relics of — 
animal organization hitherto discovered. Many kinds of 
Crinoidea abound in the Silurian rocks, and one genus of — 
Star-fishes occurs in the same deposits: the Echinidee first 
appear in the Devonian formation. 
* The impression of an Acaleph resembling an quorea (a kind of 
Medusa), is stated by M. Pictet to have been observed in a slab of 
schistose rock, in Germany. 
a Se eee ee 
