SILURIAN RADIATA. 169 



To the naked eye the whole of the tubular structure of this 

 coral is manifestly coarser than in the N. lens, from which it 

 differs in its large irregular foliaceous expansions of growth ; it 

 also seems that the proportion (150 to an inch) of small cells in 

 a given space was also greater in the F. (Nebulipora) favosa 

 (Phill. sp.), to which I should have otherwise referred it. 



Coniston limestone, Coniston. 



[Col. University of Cambridge.) 



Nebulipora lens (M'Coy). 

 Sp. Char. Corallum forming lenticular masses averaging 10 lines 

 in diameter and 1^ line thick in the middle, gradually thin- 

 ning to the edge ; base slightly concave, with small concentric 

 wrinkles ; upper surface evenly convex ; clusters of large cells 

 rounded, flat or slightly concave, about 1 line in diameter and 

 usually a little more than their diameter apart (averaging from 

 sixteen to twenty cells between one centre and another) ; 

 smaller tubes averaging eight in one line, larger tubes of the 

 clusters averaging four or five in one line; two interdia- 

 phragmal spaces equal the diameter of the tube; apparently 

 two irregular^ close rows of connecting pores on each face of 

 each tube. 



When imperfectly developed or rubbed, it is difficult to recog- 

 nize the imperfect star-like clusters or nebulae of the larger tubes. 

 The structure not being composed of concentric layers round a 

 central nucleus, and the appearance of the mouths of the tubes 

 on the upper surface, easily distinguish this fossil from the Stro- 

 matopora nummulitisimilis (Lonsd.). 



Owing to the minuteness and imperfect mode of preservation 

 it is difficult to be satisfied about the connecting pores, but from 

 the appearance under a high power of several specimens, I have 

 little doubt they are as in the above notice. 



In great abundance clustered like Nummulites in some parts of 

 the fine Caradoc sandstone of Horderly West ; more rare in the 

 schists of Moel Uchlasi'; Pont y Glyn, Diffwys; Cwra of the 

 Cymmerig. 



{Col. University of Cambridge.) 



Nebulipora papillata (M'Coy) . 

 Sp. Char. Corallum forming very thin layers (usually coating 

 Orthoceratites) ; clusters of large cells elevated into conical 

 papillae, about ten in each cluster ; the papillae a little wider 

 than high, usually about twice their diameter apart, quincun- 

 cially arranged ; thickness of corallum usually less than half a 

 line, diameter of papillae about half a line, distance apart 

 about one line ; of the smaller cells about nine or ten occupy 

 one line. 



