Explanation of Plates. 



PLATE I. 



Figs. 1-12. Spicules of Lysactinella G-ehhardi, as shown in a section througli 



the sponge. X 30. 

 Figs. 14-17. Spicules of Lysactinella Gebhardi preserved as casts in a phos- 



phatic nodule. X 30 . 

 Figs. 13, 18-21. Spicules of Lysactinella Gebhardi preserved free as pyrite. 



X 30. 



Figs. 22-31. Spicules of Lysactinella perelegans preserved as pyrite. x 30. 



