EXPLANATION OF PLATE XVII. 



Hyalonema rapa. F. E. Sch. 



Fig. 1. Lateral view of a specimen. Nat. size. 



Fig. 2. Arrangement of the spicules in a transverse section of the upper 

 marginal region, vertical to the surface x 50 (combined figure). 

 Fig. 3. Large, curved oxydiactine. x 20. 



Figs. 4 and 5. Intermediary parenchymal oxyhexactines. x 800. 

 Fig. 6. Dermal pinule. x :^00. 

 Fig. 7. Oanalar pinule. x 300. 

 Fig. 8. Gastral pinule. x 300. 

 Figs. 9 and 10. Mesamphidiscs. ^ 300. 



Figs. 11 and 12. Micramphidiscs seen from the side and from above. 

 X 300. 



Fig. 13. Macramphidisc. x 200. 



