Fig. 8

Enlargement from Fig. 7 showing details of structure of Labechia carbonaria in thin section. Both photographs are in cross-polarized light, in which the structure is easier to see in these rather thick sections; therefore dark areas of the pictures are portions of calcite crystals in extinction. Narrow slightly irregular short dark lines are fractures in the structure, presumably from the grinding process that has partly broken the rock slices in these particular samples. a Vertical section of pillars and cyst plates and interstitial cement. All four pillars illustrated here show the micritic structure (compact microstructure) of the skeleton, that has a faint downward-pointing chevron-form pattern of indistinct laminations merging along the centre line. Note that the structure of L. carbonaria lacks the curved cone-in-cone type of architecture illustrated in Fig. 10 for Labechia conferta; b Transverse section showing pillars and indistinct cyst plates with interstitial cement. Pillars in TS reflect the chevron-form pattern (shown in a) by density variation in the pillars. The arrow shows one pillar with a lighter centre and darker rim, presumably a concentric feature of the chevron pattern. a is Sample number NHMUK PI S 10490$1; b is sample number NHMUK PI S 10491$1. Photos taken by the authors