Plate XVI. 



Fig. I. Interambulacral area of Stereocidaris ingolfiana. ^U. 



'— 2. — — - Echiiiiis acutiis, var. Fleniingii. 7,. 



— 3. Apical area of Echinns elegans. ^i- 



— 4. — — - Strongylocentrotus drøbachiensis. ^/j. 



— 5. — — - Echinus aattjis, var. Jiorvegtcus. 2/,. 



— 6. — — - — afjinis. ^/i. With two pores in one of the genital piates. 



— 7. — — - — esculentus. ^y,. 



— 8. — — - — Alexandri. 2/,. With two pores in two of the genital piates. 



— 9. — — - Stj-ongylocentrotiis drøbachiensis. ^/j. 



— 10. — — - Ec/nnns acntns., var. Flemingii. ^/i. 



— II. Interambulacral area of Strongylocentrotus drøbachiensis^ f. graniilaris. ^/j. 



— 12. Piates from the buccal niembrane and the gills of Echimis escnlentus. a. b. from the buccal 



membrane outside the buccal piates, c. from inside the buccal piates, d. e. f. from the 

 gills. Obj. II. Oc. III. 



— 13. Piates from the buccal membrane of Strongylocentrotus drøbachiensis. a. outside, b. inside the 



buccal piates. Obj. II. Oc. III. 



— 14. Plate from the buccal membrane of Parechinus microtuberculatiis. Obj. II. Oc. III. 

 -- 15- - — — — - — iniliaris. Obj. II. Oc. III. 



— 16. Piates from the buccal membrane and the gills of Echimis aczitiis, var. Flemingii. a. b. from 



the buccal membrane outside the buccal piates, c. from inside the buccal piates, d. e. f. from 

 the gills. a. b. Obj. II. Oc. L, c— f. Obj. II. Oc. III. 



— 17. Interambulacral area of Strongylocentrotns drabachioisis, i. pal /id ii s. ^j. 



— 18. Ambulacral area of Echimis aciittis, var. Flemingii. '/j. 



— 19. — — - — elegans. ^/j. 



— 20. — — . — affinis. ^/i- 



— 21. — — - Strongylocentrotus drøbachiensis^ f. gramrlaris. ^/i. 



— 22. — — - Echinns acutiis., var. ttorvegicus. ^U. 



— 23. — — - Strongylocentrotus drøbachiensis, f. pallidus. ^/j. 



