PLATE I. 



Page 

 Fig. 1. Climacospongia radiata, Hinde. Showing the interior of the sponge. Natural 



size. Drawn from a fractured surface. From Silurian strata : Tennessee . . 18 



Fig. 1 a. The same. Portion of the fractui'ed surface of the same specimen, showing the 

 radiating and transverse spicules. Enlarged twelve times. 



Fig. 2. Lasiodadia compressa, Hinde. Showing the spicules on the surface of a fragment 



of shale. Natural size. From the Lower Devonian at Jemelle, Belgium . . 19 



Fig. 3. Acanthoraphis intertextus, Hinde. Showing the outer surface of the sponge. 



Natui-al size. From the Upper Chalk at Shortlands, Kent 20 



Fig. 3 a. The same. Portion of the outer surface of the same specimen, showing the dispo- 

 sition of the spinous spicules. Enlarged ten times. 



Fig. 4. Ophiraphidites anastomans, Hinde. Section of a specimen, imbedded in chalk, 

 showing the disposition of the skeletal tissues. The spicules have been replaced 

 by iron peroxide. Natural size. From the Upper Chalk : South of England . 23 



Fig. 4 a. The same. Portions of straight and curved acerate spicules, from a specimen 

 inclosed in flint, from the Upper Chalk. Enlarged thirty times. 



Fig. 5. Tethyopsis cretaceus, Hinde. A fragmentary specimen imbedded in flint. Natural 



size. From the Upper Chalk : South of England 24 



Fig. 5 a. The same. Portion of the same specimen, showing the disposition of the spicules. 

 Enlarged eight times. 



Fig. 6. Stelldta iuclusa, Hinde. Filling a cavity in the interior of a flint from the Upper 



Chalk. England. Natural size 24 



Fig. 6 a. The same. Acerate and trifid spicules from the same specimen. Enlarged eighteen 

 times. 



Fig. 7. Pachastrella plana, Hinde. A fragmentary sponge inclosed in a hollow flint. 



Natural size. From the Upper Chalk at Upware 27 



Fig. 7 a. The same. Portion of the surface of the same specimen, showing the spicules. 

 Enlarged twelve times. 



Fig. 8. Renlera ? Carteri, Hinde. Detached spicules from decayed chert of Lower Carbo- 

 niferous age. Dairy, Ayrshire. Enlarged twenty-seven times 19 



Fig. 9. Spoiiffilla pwrbeckensis , Young. Microscopic section of chert filled with the spicules 

 of this species. From Purbeck strata at Stare Cove, Dorset. Enlarged fifteen 

 times 21 



Fig. 10. Microscopic section of chert from the Portland Oolite, at Upware, near Weymouth, 



showing spicules of Tetractinellid sponges. Enlarged fifteen times .... 27 



Fig. 11. Portion of the weathered surface of a sponge-bed, showing detached spicules of 

 Tetractinellid and Litliistid sponges. Enlarged thirty times. From the Lower 

 Green Sand at Haslemere, Surrey 27 



Fig. 12. Microscopic section of chert, filled with spicules of Tetractinellid sponges. Enlarged 

 fifteen times. From the Upper Green Sand, near Ventnor, Isle of Wight. 



