Revision of Pentaphyllum de Koninck, 1872 (Anthozoa, Rugosa)

Lectotypes of Pentaphyllum armatum and P. caryophyllatum, both of De Koninck (1872) have been sectioned for the first time and are completely illustrated; both are preserved as silicified outer shells with inner structures dissolved. The morphology of the calices strongly suggests that they have different taxonomic positions. Thus, their synonymy, suggested by Schindewolf (1942), is rejected. P. armatum, selected as type species for the genus by Hinde (1890) possesses six, not five leading major septa. Consequently, all taxa except Hexalasma Soshkina, 1928, and perhaps Pseudocryptophyllum Easton, 1944, are unrelated to Pentaphyllum. It is proposed to restrict the name Pentaphyllum to the lectotype. The well established Cryptophyllum Carruthers, 1919, which includes P. caryophyllatum, is considered valid. In addition to a brief analysis of Lower Carboniferous corals included here in Cryptophyllum, a few specimens from the British Tournaisian are described and illustrated to show morphological variability of specimens from the same bed. Review of earlier studies on these types of corals, discussion on the difference between zaphrentoid and cryptophylloid early ontogeny and its bearing on taxonomy, and description of taxa, are also included.