Plate XV. 



Fig. I. Ambulacral area of Eckmiis esculeutns. '/i. 



— 2. Iiiterambulacral area of Echinus aciiins, var. norvegicus. ^/j. 



— 3. — — - — affiiiis. ^/i. 



— 4. — — - — elegans. ^/,. 



— 5. — — - — esculcntiis. '/i- 



— 6. Apical area of Parcchunts iniliaris. ^j^. 



— 7. Ambulacral area of Parechiims iniliaris. ^/i. 



— 8. — — - — inicrotubercHlatns. ^/i. 



— 9. luterambulacral area of Parechiims microtiiberailattis. ^/i. 



— 10. Ambulacral area of Echinus affinis. ^/i (young specimeu). 



— II. Iiiterambulacral area of Parechinns niiliaris. ^/i. 



— 12. Apical area of Parechiims inicrotiiberculatiis. ^/i. 



— 13. Ambulacral area of Echinus Alexandri. ^/i. 



— 14. — — - — acni/is, var. mediterranea. '/i- 



— 15. Iiiterambulacral area of Echinus acutiis., var. mediterranea. '/i- 



— 16. Ambulacral area of Echinns acntits^ var. norvegicus. ^/j. 



— 17. Iiiterambulacral area of Echinus Alexandri. ^/j. 



