. Bulletin du Musée Histort naturelles. Série Géologie. ACROPORELLA ASSURBANIPALI AFFINITÉ systématique de l'oftlie 113 la variabilité des espèces et certains caractères qualitatifs tels que la forme de thalle, latérales et d'organes de reproduction aurait exigé plus abondant matériel. Le thalle est cylindrique et apparemment simple. Les canalisations secondaires primaires sont disposés en verticilles modérément fermer. Leur position entre les verticilles, alternés ou dans la continuité, n'est pas évident. Ils sont cependant plutôt phloiophorous et strong, presque perpendiculaire à l'axe de la tige. La section transversale des pores est primaire

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. Bulletin of the Natural Histort Museum. Geology series. SYSTEMATIC AFFINITY OF ACROPORELLA ASSURBANIPALI 113 the variability oftlie species and some qualitative characters such as the shape of thallus, laterals and reproductive organs would have required more abundant material. The thallus is apparently cylindrical and simple. Primary laterals are arranged in moderately close whorls. Their position between whorls, alternated or in continuity, is not evident. However they are phloiophorous and rather strong, almost perpendicular to the stem axis. The transverse section of the primary pores is rectanglar in the middle part and square in the distal part. The number of primary laterals per whorl can be estimated as 11 -12. This value corresponds well with that supplied by Elliott. Two strong secondary laterals originate from the distal end of each primary lateral. They show a subcylindrical inner part of modest length, 0.11-0.12 mm, and 0.10-0.12 mm in diameter, followed by a part that flares out quickly, so making a cortex at their distal end (pl.l, fig. 3). The two secondary laterals are nearly placed on an horizontal plane, i. e. parallel to the verticillar plane. Elliott did not identify the twofold laterals, but he interpreted the shape of primary and secondary laterals in longitudinal section as parts of a single lateral. He correctly described the first inner part (primary) as 'a fig- or flask-shaped cavity', and the second outer part (secondary lateral) as 'a slightly curved tube'. The holotype occasionally shows structures referable to reproduc- tive organs (ampullae: pi. 1, fig. 2). The ampulla is set at the distal end of each primary lateral, over the plane where the secondary laterals are placed. It is of spherical shape, 0.11 mm in diameter, joined to the primary lateral probably by means of a short peduncle. The difficulty in observing the reproductive organs can be explained by the fact that most of them were empty and were destroyed after the re-crysta

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