PLATE X. 



Page 



Fig. 1. Nematinion calyculum,'iiinie. A specimen, imperfect at the base, from the Upper 



Green Sand at Warminster, Wiltshire. Natural size 54 



Fig. 1 a. The same. Transverse section of the stem of another specimen, showing traces of 



the horizontal canals. Natural size. 

 Fig. 1 b. The same. Portion of the surface of fig. 1, enlarged eight times, showing traces 



of the spicular structure. 

 Fig. 1 c. The same. Portion of the interior of the stem, enlarged sixteen times, showing 



the character and disposition of the spicules. Drawn from the polished surface 



of a vertical section. 

 Fig. 2. Heterostinia obliqua, Benett, sp. The outer surface of an imperfect cup-shaped 



specimen with numerous root-processes. Natural size. Inclosed in a flint from 



the Upper Chalk of Wiltshire 53 



Fig. 2 a. The same. Showing the semipalmate stem and a portion of the expanded bodv- 



plate of another flint-inclosed specimen from Wiltshire. Natural size. 

 Fig. 2 b. The same. Portion of the outer surface of a specimen, in which the dermal layer 



has been preserved, showing its spicular structure. From the interior of a Chalk 



flint from Wiltshire. Enlarged sixteen times. The specimen belongs to the 



Jermyn-Street Museum. 

 Fig. 2 c. The same. Portion of the surface of a specimen, in which no dermal layer has 



been preserved, showing the spicular structure of the interior of the wall of the 



sponge. Enlarged sixteen times. 

 Fig. 3. Isoraphinia texta, Roemer, sp. From the Upper Chalk at Flamborough, Yorkshire. 



Natural size 55 



Fig. 3 a. The same. Transverse section of another specimen from the same locality, showing 



the central cloacal tube. Natural size. 

 Fig. 3 6. The same. Portion of the outer surface of fig. 3, showing traces of the exterior 



layer of spicules. Enlarged seven times. 

 Fig. 4. Mastosia neocomiensis, Hinde. Detached spicules of various sizes. Enlarged 



twenty-six times. From the Lower Green Sand at Haslemercj Surrey . . .57 



