II.—On a Specimen of Psilophyton robustius Dawson, from the Lower Devonian of Canada *

An account is given of the species Psilophyton robustius and the relevant literature is reviewed. There follows an illustrated description of a relatively well-preserved fertile, branched specimen. The morphological features of this specimen are discussed with reference to the earlier descriptions by Dawson and others. It has been found necessary to institute a new genus as Psilophyton is now apparently inappropriate for this species. The name given to this new genus is Trimerophyton , which includes the one species Trimerophyton robustius (Dawson) Hopping.