PLATE XXX. 



Page 

 Fig. \. Toulminia jurassica,'iimAe. Natural size. Showing the weathered surface of a 



specimen from the Upper Jura at Rauden, Switzerland 139 



Fi"-. 1 a. The same. A transverse section of the same specimen, showing the cloacal ca-vaty 



and disposition of the anastomosing walls iu the interior. Natural size. 

 Fig. 1 b. The same. A portion of the polished surface of 1 a, enlarged thirty times, showing 

 the spicular structure of the walls. The spicules have been replaced by calcite, 

 and only faint outlines of the rays and the octahedi-al nodes are discernible. 

 Fig. 2. Camerospongia aperta, Hinde. Natural size. From the Upper Chalk of the South 

 of England. The same specimen has been figured by Toul. Smith iu Ann. & 



Mag. Nat. Hist. 1848, vol. i. t. 14. f. 13 U2 



Fig. 2 a. The same. A median section of the same specimen, showing the funnel-shaped 



cloaca. 

 Fig. 2 b. The same. A portion of the cloacal surface, enlarged thirty times, showing the 

 spicidar structure. The spicules have been completely dissolved, and only their 

 empty casts in chalk remain. The octahedral character of the nodes is only 

 shown in a few places. 

 Fig. 3. Camerospongia subrotimda, Mant. sp. A small group of individuals, natural size, 

 from the Upper Chalk at Charing, Kent. The cloacal cavities are filled with 



the chalky matrix 1"*^ 



Fig. 4. Callodidyon angustatmn, Hinde. A specimen, somewhat worn away near the 



summit, from the Upper Chalk of the South of England. Natural size . . . 142 

 Fig. 4 a. The same. A fragment of tlie outer surface of the same specimen, enlarged thirty 

 times, showing the characters of the dermal layer. The spicules have been 

 dissolved, and are now shown by red markings of iron peroxide. 

 Fig. 4 b. The same. Showing the structure of the interior of the wall. Enlarged thirty 

 times. The minute tiibcrcles produced by the fiUcd-in moulds of the octahedral 

 nodes are only partially preserved. 

 Fig. 5. Porochonia simplex, T. Smith, sp. A specimen from the Upper Chalk, which 



retains the cast of the smooth exterior membrane. Natural size 143 



Fig. 5 a. The same. A cast of the dermal layer of another specimen from the Upper Chalk. 

 Enlarged thirty times. The apertures in the dermal layer have been infilled 

 with the chalky matrix. 

 Fig. 5 6. The same. Showing the spicular structure of the interior of the wall of 5 «. 

 Enlarged thirty times. The spicules are only indicated by empty moulds iu 

 the chalk. 



