PLATE XXVI. 



Page 



Fig. 1. Ventriculites infundibuliformis, S. Woodward. An imperfect specimen, partially 

 imbedded in tte chalky matrix. Natural size. From the Upper Chalk of the 

 South of England 11~ 



Fio-. 1 a. The same. Transverse section of a specimen preserved in flint, showing the dispo- 

 sition of the folds of the sponge-wall. Natural size. From the Upper Chalk of 

 the South of England. 



Fio-. 2. Ventriculites cribrosus, Phillips, sp. An imperfect specimen from the Upper Chalk 



at Flamhorough, Yorkshire. Natural size 113 



FHg. 2 a. The same. Part of a transverse section of another specimen from Flamborough, 

 showing the folds of the wall. Natural size. 



Fig. 3. Ventriculites angustatus, F. A. Roemer, sp. An imperfect silicified specimen from 



the Upper Chalk, South of England. Natural size 114 



Fi°-. 3 a. The same. The upper portion of fig. 3, showing the thickness of the wall and the 

 canal-apertures of its inner surface. Natural size. 



Fig. 3 b. The same. A small portion of the outer surface of fig. 3, enlarged eight times, 

 showing the canal-apertures and the perforated dermal layer. 



Fi"-. 4. Sporadoscinia capax, Hinde. An imperfect example from the Lower Chalk, two- 

 thirds the natural size, showing a fragment of the sponge-wall, with some oysters 

 attached to a part of its surface, and impressions of the canal-apertures of the 

 inner or cloacal surface. From the South of England 116 



Fig. 4 a. The same. Portion of the outer surface of fig. 4. Enlarged eight times. 



Fig. 4 b. The same. Portion of the interior of the wall of fig. 4, enlarged thii-ty times, showing 

 traces of the spicular mesh. Drawn from a fractured surface. The spicules have 

 been completely dissolved, and only the empty moulds in the chalky matrix 

 remain. 



