OF THE GENUS MICROCIOXA. 



entirely spined. Interstitial membranes tliin and pellucid ; spicula 

 same as dermal membrane. Habitat, Paignton Rocks, Torbay. 



DESCRIPTION OF PLATES I. AND II. 



Plate I. 

 Fig. 1. — JMicrociona bihamigera. Sponge fall size, coating a piece of the 



New Red Sandstone- 

 Fig. 2. — Spicule of skeleton. 400 diam. 

 Fig. 3. — Smaller ditto. 400 diam. 



Fig. 4. — Cylindrical spicule of dermal membrane. 400 diam. 

 Fig. 5, 6. — Groups of bihamate andanchorate spicules from the membranes. 



725 diam. 

 Fig. 7. — Portion of the dermis showing the arrangement of bihamate 



spicules. 80 diam. 

 Fig. 8. — Tridentate, equi-anchorate, palmate spicule of the membranes. 



1150 diam. 

 Fig. 9. — Bidentate ditto. 1150 diam. 

 Fig. 10. — Bihamate ditto. 725 diam. 



Plate II. 

 Exhibits a section of the sponge at right angles to its surface, showing, 

 arrangement of the skeleton columns. Some of these are dis- 

 rupted from their bases of attachment, a, shows reticulation of 

 dermal membrane, and some spicules projecting through the 

 latter. 80 diam. 



