FOSSIL ECHINOOEKMS. 
415 
SECTION I. 
FOSSIL ECHINODERMS. 
The animals that compose this highest Class in 
the grand division of Radiated animals, viz. 
Echinidans, Stelleridans, and Crino'ideans, have, 
hll lately, been considered as made up of many 
^itnilar parts disposed like Rays around a com- 
®ion centre. 
Mr. Agassiz has recently shewn, (London and 
Edin. Phil. Mag. Nov. 1B34, p. 369), that they 
not partake of this character, from which the 
division of radiated animals is named ; but that 
their rays are dissimilar, and not always con- 
nected with an uniform centre ; and that a bila- 
teral symmetry, analogous to that of the more 
perfect classes of animals, exists throughout the 
families of Echini, Asteriae, and Crinoidea. 
echinidans and stelleridans. 
The History of the fossil species of Echinidans 
nnd Stelleridans has been most beautifully illus- 
trated, in the plates of the Petrefacten of Prof, 
tjoldfuss. Though derived from Strata of various 
degrees of high antiquity, they are for the most 
part referred by him to existing Genera. 
The family of Echinidans appears to have ex- 
