Charles Doolittle Walcott,
New Species of Trilobite from the Trenton Limestone at Trenton Falls…
(1875)
“ Thorax with ten segments arching forward, narrows rapidly to the pygidium; axial lobe separated from the plural lobes, by a sharp ridge extending two-thirds the distance across each segment, a slight diagonal furrow crosses the segments of the axial lobe near the junction of the axial and plural lobes. ”
