Re-assessment of the type collections of Maslov's species of Hapalidiales (Rhodophyta). Species originally attributed to Lithothamnium, Mesophyllum and Palaeothamnium

This is the third and last paper of a series devoted to the revision of the types of the species and infra-specific taxa of coralline red algae established in two monographs by Maslov. Maslov's new species and intraspecific taxa were separated by characters of questionable significance from a modern taxonomic point of view. In this study, as un previous contributions, a number of types of fossil coralline algae Maslov's original collection are re-assessed with a modern morpho-anatomic taxonomic approach. This paper deals in particular with the types of species attributed of Maslov to the genera Lithothamnion (as Lithothamnium), Mesophyllum and Palaeothamnium (Hapalidiales, Rhodophyta). According to our reassessment, only the type of Mesophyllum schenckii var. corticesum can be confidently assigned to a currently accepted genus within the family Hapalidiaceae, subfamily Melobesioideae. The types of Lithothamnion iorii, Palaeothamnium kassovense, Mesophyllum kutense, Lithothamnion microcellulosum, Lithothamnion praefructiculosum, and Lithothamnion thcernomoricum possess multiporate conceptacles and non-coaxial ventral core and can be attributed to the subfamily Melobesioideae. The lack of ephitallial cells, however, prevents any precise generic assignment within the Lithothamnion, Phymatolithon, Clathtomotphum and Synarthrophyton complex. Finally, the lack of significant characters prevents any confident attribution of the type of "Lithothamnion saxorum var. korolukae" to any defined generic or suprageneric taxon within the Hapalidiales or the Corallinales. The absence of reproductive structures int ye types of "Lithothamnion caucasicum", "Lithothamnion (?) intergeminum" and "Lithothamnion (?) suhumii" prevents the placement of these taxa in any order and family within Hapalidiales, Corallinales or Sporolithale