PORIFERA. 145 



The structure of most of our species is illustrated by the work 

 of Prof. Sollas upon the ' Catagmidse ' \ 



Whatever may have been the original constitution of these 

 sponges they must have been originally hard and rigid, for large 

 Serpula and other episites often affixed themselves to them. The 

 fibre is well seen in the coarse-formed Pachytiloda, shewing simple 

 spicular fibres, having no relation with the Lithistida. 



The name Catagma (Sollas) is here used by me in a more 

 restricted sense than that originally proposed by the author, whose 

 diagnosis seems to me to include too large and diverse a group for a 

 single genus. Therefore I have followed Zittel in retaining the old 

 name Elasmostoma for such osculated forms as E. pezisa and 

 E. macropora, and I adopt Catagma for the remaining Upware 

 forms without distinct oscules, as C. cupuliformis and G. porcatum. 

 A new name was necessary for the latter group because of the 

 previous confusion, but the former genus Elasmostoma has re- 

 mained a well-defined and, as I think, natural genus since its first 

 establishment ^ 



Hexactinellida. 



Plocoscyphea pertusa, Geinitz, das Elhthale Bachsen, i. p. 26, 

 pi. II., f. 5. 



(Plate VIII., fig. a, h) 



The hexactinellid structure of this sponge is beautifully pre- 

 served in carbonate of lime, and in places it is well seen left in 

 relief. 



Locality. Brickhill. 



N. Europe. Near Dresden (Untersten Planer). 



Verticellites anastomosans, Mantell, Medals of Creation, 



p. 227. 



See Sharpe, Quart. Journ. Geol. Soc, x., p. 195, pi. v., f. 1. 

 Localities. Upware, Brickhill, Farringdon, Godalming, Ather- 

 field. * 



S. Europe. Ardennes. 



1 Annals and Magazine of Natural History, Nov. 1878. 



2 Professor Sollas writes me his entire approval of the arrangement here made. 



K. 10 



