Plate XVI. 



Fig. i. Interambulacral area of Stereocidaris ingolfiana. 2 / I . 



2. - Echinus acutus, var. Flemingii. /i- 



3. Apical area of Echinus elegans. 2 / r . 



4. - Strongylocentrotus dr0bachiensis. 2 / t . 



5. - Echinus aciitus, var. norvegiciis. 2 /j. 



6. affinis. 2 / I . With two pores in one of the genital plates. 



7. esculentus. 2 /,. 



8. Alexandri. 2 /i- With two pores in two of the genital plates. 



9. - Strongylocentrotus dr0bachiensis. 2 / I . 



- 10. - Echinus acutus, var. Flemingii. 2 / I . 



ii. Interambulacral area of Strongylocentrotus drobachiensis, f. granularis. 2 / : . 



12. Plates from the buccal membrane and the gills of Echinus esculenttts. a. b. from the buccal 



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

 gills. Obj. II. Oc. III. 



- 13. Plates from the buccal membrane of Strongylocentrotus dr0bachiensis. a. outside, b. inside the 



buccal plates. Obj. II. Oc. III. 



14. Plate from the buccal membrane of Parechimis microtuberculatus. Obj. II. Oc. III. 



- 15. miliaris. Obj. II. Oc. III. 



- 16. Plates from the buccal membrane and the gills of Echinus acutus, var. Flemingii. a. b. from 



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

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



- 17. Interambulacral area of Strongylocentrottis drebachiensis, f. pallidus. 2 / I . 



- 18. Ambulacral area of Echinus acufus, var. Flemingii. I / I . 



19. elegans. 2 / r . 



- 20. affinis. 2 / t . 



- 2i. - Strongylocentrotus drobachiensis, f. granularis. 2 / r . 



- 22. - Echinus acutus, var. norvegicus. 2 / I . 



- 23. - Strongylocentrotus drebachiensis, f. pallidus. 2 / t . 



