'.o6 



ZOOLOGY 



urchin of the Maine coast (Fig. 247) — grind out pockets in 

 the rocks bj' means of their spines. Others cover themselves 

 with seaweed, and thus become inconspicuous. Besides the 

 green sea-urchin, wliich is found north of Cape Cod, we have 

 a black sea-urchin (Arbacia), which extends south as far as 



Fig. 247. — Stronffylofetitrotus, the Eastern green sea-urchin, with tul^e 

 feet extended. From "Standard Natural History." 



North Carolina. We have on the east coast also two kinds of 

 flat sea-urchins (sand-dollars), which live in the sand from low 

 water to one hunrlred fathoms. Their spines are small and 

 silky (Fig. 24S). 



The sea-cucumbers, or Holothurians,i may be hkened to soft- 

 skinned sea-urchins, with the body drawn out to the form of 

 a cucumber, or even of a worm. The limy skeleton is reduced 



^holothurion, a sort of water polyp. 



