ECHINODERMATA 



1. Echinus. Ventral view of live animal: peristomial membrane with mouth; teeth; ten branchial 

 plumes of peristomium (diverticula of body-cavity). 



2. Shell of Echinus cleaned. Dorsal view : anal opening ; periproct ; genital plates with genital 

 openings, one of them perforated by the water pores of the madreporite ; ocular plates ; five double 

 rows of ambulacral plates with ambulacral pores for the tube-feet; five double rows of interambulacral 

 plates ; tubercles to which the spines are articulated. 



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