444 



MERISTIC VARIATION. 



[part I. 



II 



Fig. 137. Echinus melo, No. 680, having the right posterior ambulacrum 

 partially absent, a, anterior ambulacrum, ra, la, right and left anterior ambu- 

 lacra, rp, Ip, right and left posterior ambulacra. I. View from apex. II. View 

 from oral surface. (From Philippi.) 



