PLATE XXIX. 



Page 

 Fig. 1. Cmloscyphia sulcata, Tate. Natural size. From the Spongarian zone of the 



Chloritic Chalk [Tate) ( = Upper Chalk), Whitehead, near Belfast. The speci- 

 men belongs to the Jermyn-Street Museum 118 



Fig. 1 a. The same. The upper surface of the central stem of fig. 1, enlarged three times, 

 showing the foldings of the wall and traces of the spicular mesh. 



Fig. 2. Plocoscyphia labrosa, T. Smith, sp. Natural size. An average specimen from the 

 Upper Green Sand near Folkestone, showing the disposition of the folds of the 

 wall 133 



Fig. 3. Plocoscyjjhia reticulata, Hinde. A specimen from the Upper Green Sand at East- 

 bourne, partially imbedded in a marly matrix, sliowing in the upper portion the 

 apertures of several tubes with the canal-openings in their walls, and in the 

 lower portion sections of the tube-walls. Natural size 135 



Fig. 3 a. The same. A fragment of the dermal layer of a specimen from the Chloritic Marl 

 at Rocken End, Isle of Wight, showing one or two of the canal-openings and the 

 smaller apertures of the spicular mesh. Enlarged thirty times. 



Fig. 3 b. The same. Three fragments of the spicular mesh of the interior of the wall of 3 a, 

 enlarged thirty times, showing the octahedral or lantern nodes, and traces of 

 canals in some of the spicular arms. Drawn by means of the camera lucida. 



Fig. 4. Plocoscyphia fiexmsa, Mant. sp. A fragment of the spicular mesh of the interior 

 of the wall, enlarged thirty times, showing the octahedral nodes. The siliceous 

 structure of the specimen has been completely replaced by iron peroxide. From 

 the Upper Chalk of the South of England 136 



Fig. 5. Plocosc7jphia labyrinthica, Mant. s]^. A specimen imbedded in a flint which shows 

 on its upper surface, in section, the anastomosing folds of the wall, indicated by 

 markings in iron peroxide. Natural size. From the Upper Chalk at Offham, 

 Kent 137 



Fig. 6. Plocoscyphia vagans, Hinde. A nodule of chalk, showing on its surface the 



anastomosing wall-plaits. Natural size 137 



Fig. 6 a. The same. A fragment of the spicular mesh of fig. 6, enlarged thirty times, 

 showing the octahedral nodes. The spicular mesh is now in the condition of 

 iron peroxide, and its surface is rough and uneven. 



Fig. 7. Tuulminia obliqiia, Iliude. A median section of a specimen from the Upper Chalk, 



showing in section the disposition of the interior wall-plaits. Natural size . . 139 



Fig. 7 a. The same. A transverse section of fig. 7, showing the wall-plaits as seen from 

 above. Natural size. 



Fig. 7 b. The same. The summit of fig. 7, showing the wall-plaits, which are exposed by 

 the removal of the dermal layer. The walls in this specimen are indicated by 

 markings in iron peroxide. 



