PORIFERA. 149 



Cory N ELLA, sp. 

 (Plate VIII., fig. 5.) 



This is likely to be the young of G. nodosa, Kpng. 

 Locality. Brickhill. 



Peronella furcata, Goldf., sp. 



Scyphea furcata, Goldfuss, Petr. Germ, i., pi. il, f. 6, p. 5. 



Polyendostoma furcata, Romer. 



Gnemidium astrophorum, Mantell, Medals of Creation, p. 227. 



Localities. Brickhill, Farringdon. 

 N, Europe. Essen. 

 S. Europe. Ardennes, Mont Sal^ve. 



Pachytiloda, Zittel. 

 (Plate VIII., fig. 6.) 



A remarkably coarse sponge structure, with open meshes 4 mm. 

 across, and even some of them as much as three-quarter in. long. 



Diameter of fibres variable (1 — 3 mm.). 



The fibres usually form an irregular network, but sometimes 

 expand into lamellae; numerous fibres may thus unite to form 

 plates running in any direction. 



The most perfect specimen, from Brickhill, is a hemispherical 

 mass, about two inches in diameter. The basal fibres are fused into 

 an irregular lamina, fixed to fragments of rock for attachment ; 

 patches of lateral surface laminae were also locally developed, and 

 irregular plates are included in its substance. 



There is no trace of canals, oscules, or cloaca, the water circula- 

 tion having apparently no definite courses. 



Gonstitution of the fibre. The Up ware specimens, which are 

 of chalky consistency, exhibit the coarse fibres as made up of 

 delicate curved filaments (spicules) lying parallel with each other 

 and arching out from the centre towards the circumference, thus 

 presenting the appearance of a branch of small-celled Chcetetes. 

 This structure is visible to the naked eye, and is best seen with a 

 pocket lens. 



