LABECHID&. 



33* 



surface being covered by a concentrically - striated epitheca. 

 Upper surface covered with rounded or elongated, sometimes 

 partially confluent, tubercles, which are quite solid, and are 

 separated by an imperforate calcareous membrane. In internal 

 structure, the corallum consists of a great number of cylindrical 

 calcareous columns, which are directed vertically upwards from 

 the basal epitheca, and the upper ends of which constitute the 

 surface-tubercles above mentioned. The columns sometimes 

 appear to be solid throughout ; sometimes they exhibit more or 

 less distinct traces of a minute central tube ; so far as certainly 

 observed, they are apparently solid at their upper ends. The 

 interspaces between the columns are occupied by a series of 

 lenticular vesicles, the convexities of which are directed up- 

 wards, and the uppermost layer of which gives rise to the 

 seemingly imperforate membrane which forms the whole of the 

 upper surface between the tubercles. 



Obs. The genus Labechia was originally founded by Milne- 

 Edwards and Haime for the reception of the singular L. con- 



Fig. 44. Labechia conferta, E. and H. A, A small specimen from the Upper Silurian ol 

 Gotland, of the natural size. B, Portion of the upper surface of the same enlarged, show- 

 ing the surface-tubercles, c, Part of a vertical section of the same, enlarged : <z, the cal- 

 careous columns represented as opaque ; b, the lenticular vesicles, filled with calcite. 



ferta of the Upper Silurian rocks, which is still the only de- 

 scribed species of the genus. As to the structure and affinities 

 of Labechia, the French authors regarded it as referable to the 

 ChcetetintB) and they describe it as having a corallum with con- 

 fluent and not distinct calices, the " visceral chambers filled up 



