PALAEOZOIC CORALS AND FORAMINIFERA. 89 



mode of growth, had a community of existence and organic 

 union at the surface ; and from the same cause the columns have 

 no outer surface to exhibit in a rough fracture, but break 

 through the middle rather than separate one from another. In 

 the Stylaxis however, as in the StylastrcBu, the new columns are 

 produced by a sudden splitting of one of the columns into two, 

 the divisional lines commencing along the middle of one face and 

 going directly across to the opposite face, distinctly separating 

 the young four- sided column at once by a double-plated, recti- 

 linear boundary-wall parallel with one of the faces ; the external 

 strise of the old column being traceable upwards into the young 

 one. The columns are easily separable one from another in the 

 rough fracture, and the polyps are inferred to have been distinct 

 from each other, and each to have constructed independently its 

 own boundary-wall. 



Stylaxis major (M'Coy). 



Sp. Char. Tubes averaging 6 lines in diameter, mostly hexago- 

 nal, external surface coarsely striated longitudinally and trans- 

 versely marked with strong curved irregularities of growth, 

 the convexity of the curves upwards : horizontal section, sixty- 

 three slender radiating lamellse converging from the walls to- 

 wards the flat central style or axis, which is about 1 line in 

 width ; one half of the lamellse reach the centre, the inter- 

 vening ones reach half way ; outer area exhibiting numerous 

 transverse vesicular plates between the radiating lamellse : ver- 

 tical section, axis straight, ribbon-like; inner area broad, of 

 slightly curved vesicular plates forming rows of lengthened 

 irregular cells, extending obliquely downwards and outwards 

 from the axis, about three in a row ; outer area of rows of 

 small hemi spherically-curved plates, including small rounded 

 cells extending very obliquely upwards and outwards, about 

 six in each row. 



This species is remarkable for the large size of its tubes and 

 great number of the radiating lamellse. 



From the carboniferous limestone of Derbyshire. 

 {CoL University of Cambridge.) 



Stylaxis Flenningii (M^Coy). 



Sp. Char. Corallum of very long, prismatic, generally hexagonal, 

 easily separable tubes, averaging 3 lines in diameter ; outer 

 surface strongly striated longitudinally, and marked with di- 

 rect transverse rugosities of growth ; bipartite division of the 

 columns frequent : vertical section exhibiting the thin flat axis 

 surrounded by an inner zone of small vesicular plates inclining 



