206 HOMOLOGIES. 
cation of their structure, with the succession of 
the fossil ones. Of the five Orders, Beches-de-Mer, 
Sea-Urchins, Star-Fishes, Ophiurans, and Cri- 
noids, — or, to name them all according to their 
scientific nomenclature, Holothurians, Echinoids, 
Asterioids, Ophiurans, and Crinoids,— the last- 
named are lowest in structure and earliest in 
time. Cuvier was the first naturalist who de- 
tected the true nature of the Crinoids, and 
placed them where they belong in the classifica- 
tion of the Animal Kingdom. They had been 
observed before, and long and laborious investi- 
gations had been undertaken upon them, but 
they were especially baffling to the student, be- 
cause they were known only in the fossil condi- 
tion from incomplete specimens; and though 
they still have their representatives among the 
type of Echinoderms as it exists at present, yet, 
partly owing to the rarity of the living specimens 
and partly to the imperfect condition of the fossil 
ones, the relation between them was not recog- 
nized. The errors about them certainly did not 
arise from any want of interest in the subject 
among naturalists, for no less than three hundred 
and eighty authors have published their investi- 
gations upon the Crinoids, and the books that 
have been printed about these animals, many of 
which were written long before their animal na- 
ture was suspected, would furnish a library in 
themselves. 
