The neotypification and status of Mesophyllum (Corallinaceae, Rhodophyta)

Neotype specimens for Mesophyllum lichenoides (Ellis) Lemoine, the type species of Mesophyllum Lemoine (Corallinaceae, Rhodophyta) have been designated and critically examined, and the concept and status of the genus have been reassessed. All efforts to rediscover the original Ellis collection, which was sold at auction in 1791, have failed, and consequently a neotype was chosen from recently collected specimens from Cornwall (England). A detailed morphological and anatomical account of the neotype plants is provided, and the resulting data suggest that Mesophyllum can be distinguished from other genera of the Melobesioideae by the occurrence of a core of filaments where the cells are arranged in a coaxial manner. Nomenclatural and taxonomic data relating to Mesophyllum and its type species are presented along with relevant historical data and a brief consideration of the relationships of M. lichenoides to other species of Mesophyllum and to Millepora agariciformis Pallas.