The Section of Mammals, Carnegie Museum of Natural History houses skulls from seven genera of extant lagomorphs (one ochotonid and six leporids). Described and illustrated are the external surfaces of the bones of the skull of the North American pika Ochotona princeps (Richardson, 1828) and also illustrated is the volcano rabbit Romerolagus diazi (Ferrari-Pérez, 1893). Comparisons of selected craniomandibular features are made between O. princeps, R. diazi, and the following additional leporids: Pronolagus crassicaudatus (I. Geoffroy, 1832), Lepus capensis Linnaeus, 1758, Oryctolagus cuniculus (Linnaeus, 1758), Sylvilagus nuttallii (Bachman, 1837), and Brachylagus idahoensis (Merriam, 1891). Also included in the comparisons based on published descriptions are the following extinct taxa: Prolagus, the Sardinian pika, a Quaternary ochotonid; Palaeolagus, a late Eocene-Oligocene stem lagomorph; Mimolagus, an early Oligocene mimotonid; Mimotona, a Paleocene mimotonid; Gomphos, an early Eocene stem lagomorph; and Rhombomylus, an early Eocene eurymylid. Characters are identified that support various hypotheses of phylogenetic relationships among the studied taxa.