134 MARINE ANIMALS OF MASSACHUSETTS BAY. 



Fig. 181. 



Fig. 180. Young Sea-urchin older than Fig. 179 ; 1 1' tentacles, s" s'" spines. 



Fig. 181. Still older Sea-urchin ; 1 1 tentacles, a iiuus, p pedicellariic ; shell one si.\tceuth of aa inch 

 in diameter. 



