A high degree of morphological variability exists within Lomatium (biscuitroots, Apiaceae). This variability has led to conflicting opinions regarding relationships of white-flowered Lomatium specimens from southern Idaho and Oregon allied to L. nevadense and L. foeniculaceum. An initial morphological study, using morphometric analysis and phenetic classification techniques, suggested that these anomalous specimens, generally referred to as L. ravenii, were more closely related to L. foeniculaceum than to L. nevadense. Phylogenetic analyses using the rps16 intron, ITS, and rpl32-trnL_UAG placed five populations of the anomalous individuals within a clade including L. ravenii and the three varieties of L. foeniculaceum from our region. However, two populations collected from Succor Creek in southeastern Oregon clustered independently of L. ravenii, suggesting a new cryptic species. Subsequent morphological analyses revealed differences in morphology between L. ravenii and the Succor Creek populations. We propose a new Succor Creek endemic species, L. bentonitum.