Psammina inflate Earland-Bennett & D. Hawksw. and P. simplex Earland-Bennett & D. Hawksw. are described as new species from coccoid green algae and crustose or leprose lichens in lowland Britain. Additional records and hosts for P. stipitata are reported, and a key to the four species now known in the British Isles is presented. Psammina simplex is the more strongly pathogenic of the species, eventually destroying its hosts. The discovery of these new sp cies adds weight to the view that the genus is more appropriately regarded as a hyphomycete rather than an acervular coelomycete. The size, shape and septation dimensions of the conidial arms were found to be the most reliable characters for specie separations in the genus. Pycnopsammina lobariae Diederich & Etayo is also cited from the British Isles for the first time.