The new saxicolous species introduced by Josiah Lowe from his collections from the Adirondack Mountains, New York are reassessed. Lecidea albonigra J. Lowe, L. columnata J. Lowe, L. furva J. Lowe, L. humilis J. Lowe, L. marciensis J. Lowe, L. rugosa J. Lowe, L. soredifera J. Lowe, L. suberratica J. Lowe, and L. subramosa J. Lowe are reduced to synonymy with other, previously described taxa and must be removed from the North American lichen checklist. Lecidea nemoralis J. Lowe is a member of the Lecidea hypnorum group closely allied to L. ahlesii (Körb.) Nyl., and is here treated as L. ahlesii var. nemoralis. The status of some other lecideoid lichens in North America is also reassessed and L. marylandensis H. Magn. is shown to be a synonym of Miriquidica leucophaea (Rabenh.) Hertel & Rambold, Lecidea planetica Tuck. ex Willey to be a synonym of Micarea erratica, and the single North American collection of Micarea melanabola is shown to be a misidentification of Lecidea tugidula Fr. The new combination Porpidia subsimplex (H. Magn.) Fryday is made and shown to be an earlier name for P. tahawasiana Gowan. Lecidella subviridis Tønsberg, Toninia squalescens (Nyl.) Th. Fr., and the lichenicolous fungus Endococcus verrucosporus Alstrup are reported for the first time from North America, and Micarea elachista (Körb.) Coppins & R. Sant. is confirmed as occurring in North America. The author citations of four species described by Willey in the Appendix of Tuckerman's Synopsis of North American Lichens (Biatora furvonigrans, B. meadii, Lecidea micytho, and L. planetica) are corrected to Tuck. ex Willey.