Exploration of the Colorado River of the West and Its Tributaries Explored in 1869, 1870, 1871, and 1872, Under the Direction of the Secretary of the Smithsonian Institution.

Page 278, Exploration of the Colorado River

278 EXPLORATION OF THE CANONS OF THE COLORADO. vertical plane of incisors; rostrum broad, parallel-sided. Parietals small, linear, remote from the orbits. Occipital of an ordinary character, not attaining top of skull. Temporal bone, though of great extent, not remarkably inflated. Squamosal roofing most of the cere-* bral cavity. Zygomata of an ordinary character, with the usual connections. Tympanic, a contracted tube. Petrosals discrete from each other, in contact with basi-occipital. Mastoid excluded from roof of cerebral cavity. Zygomatic process of maxillary a plate with merely thickened upper border. cisofk; rostrum attenuated, tapering. Parietals large right-angled triangles, together as broad as the frontal, reaching orbits. Occipital reduced and of peculiar shape; a part of it mounting the top of the skull. Temporal bone unique in its enormous size and inflation, being blown up like a bladder; the swollen mastoids forming most of the occipital plane; the two temporals larger than all the rest of the skull together.* Squamosal restricted to the orbit. Zygomata thread-like in most of their extent, and greatly depressed in position; the malar bone abutting * against the tympanic. Tympanic, an inflated vestibule. Petrosals in mutual contact at their extremities, and fissured away from basi-occipital. Mastoid roofing most of cerebral cavity. Zygomatic process developing into a shield over much of the orbital space. Palatal outline strongly ascending Palatal profile nearly straight and * If the sense of hearing of Dipodomys be co-ordinated with the osseous development of fche auditory apparatus, it must bo extraordinarily acute.