The intriguing papers of M. L. Fernald and W. C. Steere upon the critical vascular plants and bryophytes of the Keweenaw Peninsula had aroused the interest of the writer as a student. There seemed to exist a possibility that the lichen flora might also reflect a comparable series of critical distribution records. It was not until considerably later, during the summer of 1947, that the opportunity of collecting in this area became a reality. Only eight days were available for work in the field but the critical localities had been so well defined in the papers of Dr. Steere that concentrated use of time was possible and many lichens were garnered during the first week of August, 1947. Some 520 collections of lichens were made, including 186 species or 226 species, forms and varieties. Of these six do not appear to have been hitherto reported from North America; these are Alectoria jubata var. cana, Candelariella reflexa, Lecanora alphoplaca, Lecidea trochodes, Pertusaria discoidea and Pertusaria ocellata ssp. andersiana. A very considerable number, including those above have not been previously reported from Michigan. These additional reports are partly based upon a different classification system from previous papers on this general area. That is, some of the more recent works used were upon e. g. Cladonia, Lecanora and Parmelia in which the species differentiations are more closely drawn and the subspecific categories are more numerous. Nevertheless, there are also among the 94 entities listed as new for the state a considerable number of well-defined species. Those included as new to Michigan are indicated by an asterisk in the annotated list of species which follows the general discussion. In any attempt to discover distributions analogous to those of the vascular plants and bryophytes as reported by Fernald and Steere, the lichenologist in North America is seriously hampered by the lack of monographic treatments of this much neglected group of plants. There is nothing to compare, for example, with Grout's Moss Flora of North