PORIFERA. 147 



The tissue is rather more delicate than in the other Upware 

 species. There is no well-marked epidermal layer. 

 Localities. Upware, Brickhill ? 



N. Europe. Plauen, Gamughagel, Dresden. 



S. Europe. Mont Saleve, Germigney. 



CATAGMA PORCATUM, Sharpe, sp. 



Manon porcatum, Sharpe, Quart. Journ. Geol. Soc., x., p. 196, pi. 

 v, f. 2. 



This species forms less perfect cups than the Elasmostoma 

 acutimargo, large expansions and folded plates being most frequent. 

 Still the cup is its proper plan of growth, and very perfect cups do 

 occur. 



The outer surface is covered with irregular, wart-like, branching 

 or crumpled prominences, which may assume an imperfect radi- 

 ating arrangement towards the margin ; its surface shews the 

 simple bare vermiculate structure. On the inner surface the 

 epidermal layer is dense and compact, pierced by an infinite 

 number of pore-like current -apertures (oscules). The epidermal 

 layer is often destroyed, leaving the vermiculate structure exposed. 

 There is no definite arrangement of the oscules. 



Localities. Upware, Brickhill, Farringdon. 



ELASMOSTOMA ACUTIMARGO, Homer. 



Tragos acutimargo, Romer, Vol. n. 10, pi. xvn., f. 26. 

 Manon macropora, Sharpe, Quart. Journ. Geol. Soc., x., p. 195, pi. 

 V., figs. 3, 4. 



Very fine specimens occur of all sizes up to a cup seven inches 

 in diameter. Small specimens may be quite irregular little plates, 

 or fans, often with the oscules external ; but all our large specimens 

 are cups, though often very irregular. The outer (pore) surface is 

 smooth and simple, or with faintly marked, gentle, radiating 

 crumplings and concentric growth-lines. On the inside of the cup 

 are seen the numerous large oscules arranged in distinct rings. 

 A cup measuring 3 inches diameter and 2 inches high has eleven 

 such rings. The oscules vary in size from 1 4 mm. in diameter ; 

 and they may be simple openings, in the substance of the sponge, 



102 



