Fig. 4
From: Halysis Høeg, 1932 — an ancestral tabulate coral from the Ordos Basin, North China
Halysis from the Middle Ordovician Zhuozishan and Kelimoli Formations of the Laoshidan section in Northwest Ordos Basin, North China. a Outcrop of the thin- to medium-bedded limestone of the Zhuozishan Formation yielding Halysis; b Catenulate cross sections of abundant ‘multiple-tube’ Halysis; c Circular cross sections of abundant ‘single-tube’ Halysis; d ‘Single-tube’ Halysis and ‘multiple-tube’ Halysis unevenly scattered; e Longitudinal section of a ‘multiple-tube’ Halysis consisting of eleven tubes with each single tube about 500 μm long; f Longitudinal section of a ‘multiple-tube’ Halysis resembling an undulated sheet (arrow); g Cross section of a ‘multiple-tube’ Halysis showing circles in various sizes and filled with sparite (arrow); h Cross section of a ‘multiple-tube’ Halysis showing the laminofibrous microstructure of tube walls composed of fibrous calcite perpendicular to wall surface and the micritic fillings in interiors of the tubes; i) Oblique sections of two ‘multiple-tube’ Halysis showing elongate cross sections of tubes (arrows 1 and 2)