CHAPTER IX. 
ECHINODERMATA. 
“ Ultra magis pisces et Echinos oeciuora celent.' ! — Hot. Ep. 
J* their “ Natural History of the Echinodermata,” Messrs. Hupe and 
^’ijardin divide this vast natural group into five orders or families, 
natQ ely : 1, Adero'idm, which includes the true star-fishes ; 2, Orinoidm, 
lili eS) calcareous, stem composed of movable pieces ; 3, Ophiwne, 
having the disk much depressed, the rays simple, and furnished with 
stems ; 4, EchimAte, comprehending the animals known as sea- 
e "8 s , or sea-urchins, distinguished by their rounded form and absence 
of arms ; 5, Eolothuroidm, with soft lengthened cylindrical body, 
c ° v erod with scattered suckers. 
The Echinodermata, from the Greek words Ijivik, rough, and Zeppa, 
^ ln J indicating an animal bristling with spines like the hedgehog’s. 
1!1 y are animals sometimes free, sometimes attached by a stem, 
ex ible or otherwise, and radiating, that is, presenting an appearance 
l "° re or less regular in all its parts, after the manner of a circle or 
its form being globular, egg-shaped, cylindrical, or like a pen- 
a g°nal pi a te ; or, lastly, like a star, with more or less elongated 
bn 
tei 
a Hches, which secrete either in all their tissues or only in the in- 
gwaorit very numerous symmetrical calcareous plates of solid matter, 
betimes forming an internal skeleton or regular shell covered with 
m °re or less consistent skin, often pierced with holes, from which 
^. e feet or tentacula issue ; they are frequently furnished with appen- 
°es of various kinds, such as prickles, scales, &c. 
y The organisation of the Echinodermata is the most perfect of all 
le zoophytes, serving as a transition between them and animals of more 
