The lower carboniferous calcareous algae Mitcheldeania Wethered and Garwoodia, gen. Nov.

Mitcheldeania nicholson Wethered, the type species of this genus, is found to be built up of a mixture of three genera of algae. One of these is chosen as typical and the name Mitcheldeania becomes a synonym of Girvanella. “Mitcheldeania” gregaria Nicholson, which is not represented in the nodules of M. nichohoni, becomes the type of a new genus Garwoodia and the species of this genus are discussed.