PLATE XVI. 



Page 

 Fig. 1 . Nelumbia tuberosa, Hinde. Prom the Grey Chalk near Dover. Natural size . . 72 



Fig. 1 a. The same. A transverse section from the central portion of fig. 1, showing the 

 disposition of the vertical canals and faint traces of the radial canals. Natural 

 size. 



Fig. 1 b. The same. A portion of 1 a, enlarged thirty-two times, showing traces of the 

 spicular skeleton. The original siliceous skeleton has been replaced by calcite, 

 and where the spicules are in contact their forms have been iudistinguishably 

 merged together; occasionally, however, the separate rays can be recognized. 

 A section of a Foraminifer is also shown in the matrix of grey chalk. 



Fig. 1 c. The same. Portion of the dermal layer of a specimen from the Upper Chalk, 

 enlarged thirty-two times, showing the heads of large compound trifid spicules 

 and traces of numerous smaller ones, and also of the mesh-spicules beneath. 



Fig. 2. Polyjei'ea arbuscula, Hinde. From the Grey Chalk near Dover. Natural size . . 73 



Fig. 2 a. The same. Transverse section of one of the branches of the same specimen, 

 showing the distribution of the longitudinal canals and faint traces of the spicular 

 skeleton, which is now calcareous. The sponge is preserved in a matrix of 

 Grey Chalk. 



Fig. 3. Polyjerea lobata, Hinde. Natural size. From the Grey Chalk near Dover ... 73 



