and species of Silurian Radiata. 283 



gularly arranged clusters of similar tubes of rather larger 

 size ; tubes in contact, traversed by horizontal diaphragms at 

 regular distances (walls apparently perforated by rows of small 

 foramina). 



The Favosites favulosa (Phill.), Mem. Geol. Surv. vol. ii., is the 

 only pubHshed species I know of this genus, which differs from 

 Favosites in the clusters of enlarged tube-cells at subregular 

 intervals ; and from Stromatopora by the tubules being regularly 

 prismatic, with diaphragms (? and connecting pores). 



Nebulipora explanata (M'Coy). 



Sp. Char. Corallum forming very thin, irregularly expanded 

 laminse, upwards of 2 inches long, covered with nearly regular 

 quincuncially arranged nebular clusters of large tubes, flat or 

 slightly depressed, about 1^ line in diameter, and rather less 

 than twice their diameter apart (about twelve or fourteen cells 

 between one centre and the next) ; smaller intermediate tubes 

 about six in one line. 



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. 



Nebulipora lens (M'Coy). 



Sp. Char. Corallum forming lenticular masses averaging 10 lines 

 in diameter and \^ 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 difiicult to recog- 

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

 The sti'ucture 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 



19* 



