168 



SILURIAN RADIATA. 



Spongarium interruptum (M^Coy). 

 Sp. Char. Elliptical, proportion of width to length about 85 to 

 100, convex below or externally, concave above or internally ; 

 interior smooth, or marked with famt concentric wrinkles; 

 exterior rugged with coarse concentric undulations, entire 

 outer surface marked with sharp, subalternate, thread-like 

 striae, five or six in one line ; some of which rise at irregular 

 intervals into short, very thick, subangular, radiating ridges 

 interrupted by the concentric wrinkles and not regularly re- 

 sumed. Average length 1 inch. 



The sharp alternately large and small striae, and the short 

 irregular interrupted ridges or elongate tubercles produced by 

 the irregular prominence of some of the ridges, distinguish this 

 species readily from the others. Two of the specimens are of 

 great interest, one show^ing the attachment of the base half round 

 a bit apparently of an Orthoceratite ; the other showing for the 

 first time the thickness of the substance to be about one-sixth of 

 a line, and exhibiting the unradiated inner concave surface, and 

 the impression of a part of the peculiarly radiated exterior. 



Rare in the green micaceous quartzite (Upper Ludlow) of 

 Spital, Kendal. 



{Col. University of Cambridge.) 



Nehulipora (M^Coy), n. g. 

 Gen. Char. Corallum incrusting or forming lenticular masses, 

 with a concentrically wrinkled epitheca below; composed of 

 small prismatic tubes perpendicular or nearly so to the upper 

 surface on which they open ; among the small tubes are irre- 

 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 published 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). 



Nehulipora explanata (M'Coy). 

 Sp. Char. Corallum forming very thin, irregularly expanded 

 laminae, 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. 



