PLATE IV. 



page. 

 Figs. J — 9 Lyidium Zitteli n. sp. Detached spicules of various forms ; 



in Figs. I, 3, spicules are shown naturally attached together 51 

 Fife's. 10 — j^ Lyidium cretacea n. sp. Detached spicules. . 54 



Fig. Jj The same. Fragment of the skeleton showing four spicules 



naturally attached together . • • 54 



Figs. 14 — 2j Detached spicules of Carterella, sp. . 54 



Figs. 24 — JO Ragadinia annulata, n. sp. Various forms of the surface 



spicules . . . .58 



Figs. .3 1 — -j".^ Racodiscula and allied Genera. -Surface spicules. 60 



Fig^-3J — ^.? Plinthosella squamosa, Zittel. Detached and combined spicules 



of the skeleton. Figs. 36, 40, 42 show fragments in which 

 the spicules are combined together ... 56 



Figs. 4S — 46 The same. Differently shaped spicules of the surface layer 



of this sponge ... 56 



All the figures on tliis Plate are drawn to the same scale of 20 diameters by 

 means of the Camera lucida. 



