ECHINODERMATA OF NEW ENGLAND. 67 



of petaloid openings. Anus on edge of disk. Aristotle's 

 lantern. Development with pluteus. Ovaries five. 



III. Spatangoids. Body swollen, globular, elongated. 

 Amhulaeral zones of different lengths, and more or less 

 modified mouth and vent asymmetrical. No Aristotle's 

 lantern. Development with pluteus. Ovaries four. 



Echinoids. 



Arbacia. Body globose ; vent and mouth opposite ; 

 two kinds of spines, the larger few in number; color pur- 

 ple. Anus closed by four triangular plates. Pluteus with 

 two lateral anal rods. 



A. punclulata, Lam. 



STKONGYLOCENTROTUS. 



Strongylocentrotus. Body globose ; anus and mouth op- 

 posite. Spines of one kind, short, small, greenish color. 



