82 BRITISH STROMATOPOROIDS. 



(Fig. 13), which may in some cases be even transversely partitioned (e.g. in L. serotina; 

 n. sp. Fig. 4). The axial canals are surrounded by denser tissue arranged in 



Fig. 13. 



VJ„ K 



': O^ 



? J, 



Fig. 13. — Sections of Labechia conferta, Lonsd., enlarged twelve times. Wenlock Limestone, Benthall, 

 A. Tangential section. B. Vertical section, j> p. Radial pillars, c c. Tabular connecting-processes. 



concentric layers, but exhibiting distinct vacuities, and thus not strictly solid. 

 The superficial terminations of the pillars are for the most part apparently solid. 

 If , however, the tissue of the pillars be really cribriform, as there seems reason to 

 believe, then this apparent solidity may be only due to the fact that any superficial 

 pores are filled with the matrix. Sometimes the surface tubercles clearly show at 

 their summits a minute pit, representing the upper end of an axial canal (Plate III, 

 fig. 14), but no traces of such openings can be detected in other examples (Plate 

 III, fig. 15), and it is not impossible that the appearance of perforations may be 

 really the result of weathering. 



Dr. Gustav Lindstrom and Professor Ferdinand Roemer have given descriptions 

 of the structure of Labechia, which differ in important respects from that given 

 above. The former of these distinguished observers has described the coenosteum of 

 Labechia as consisting in its earliest stages of growth " of a very thin circular 

 disc, with concentric lines of growth beneath, and having the superior surface 

 studded with blunt spines, which radiate from the centre, and also coalesce and 



form continuous ridges During the course of growth the primitive disc of 



Labechia is increased in thickness by the addition of successive thin strata, which 

 closely conform to the subjacent fundamental crust, being elevated where the 

 spines are situated. As these successive layers leave a small space between them 

 and are in themselves very thin, they give rise to a false appearance of tabulae" 

 (' Ann. and Mag. Nat. Hist.,' ser. 4, vol. xviii, p. 4, 1876). Prof. Ferd. Roemer 

 (' Lethaea Palseozoica,' p. 543, 1883) describes the skeleton of Labechia as consisting 

 wholly of very thin horizontal lamellse, which are superimposed one above the 

 other in a continuous series, all being in practically direct contact with one another, 

 and being bent into a system of close-set conical elevations, which in the last- 

 formed layer give rise to the surface-tubercles. According to this view there are 



