ECHINODEKMATA 



8 9 



¥\c. 76. Antedon. 



An unattached crinoifl of Europe, lateral aspect. 

 Haswell's Manual.) 



(From Parker and 



to a considerable degree the power of regenerating lost parts. 

 If the viscera are lost, new viscera develop, and when the arms 



break off, as they frequently 



do, new arms are formed in 



their place. 



There are two classes of 



Echinodermata, which are 



closely related to the Cri- 



noidea, but the represen- 

 tatives of these classes are 



entirely extinct and therefore 



preserved for us as fossils 



only. These two classes are 



the Blastoidea (Fig. yj) and 

 the Cystoidea (Fig. y8)\ the former appeared in the Upper Si- 

 lurian and disappeared after the Carboniferous ; the latter arose 

 earlier, in the Lower Silurian, to disappear in the Carboniferous. 



FIG. 77. Granato- 

 crinus, one of the 

 Blastoidea; fossil. 

 (Drawn from speci- 

 men by the author.) 



FlG. 78. Echinospha- 

 rites aurantium, one ol 

 the ( '\ 5ti hi lea ; fossil. 

 (Drawn from specimen 

 by the author.) 



CLASS II. ASTEROIDEA 



The Asteroidea (Gr. aarr]p, a star, and eZSo?, form) include the 

 common starfishes. These animals are common in the tide 

 pools along the shore and on the bottom below low-water mark, 



