Page:Walcott Cambrian Geology and Paleontology II.djvu/154

98 Glabella large, subquadrangular in outline, and separated from the fixed cheeks by clearly defined dorsal furrows; its sides are nearly parallel or slightly diverging; front broadly rounded, almost transverse; surface marked by five pairs of furrows, the posterior of which extends obliquely across the posterior portion nearly to the center and separates a small triangular lobe on each side; the next two anterior pairs of furrows are short and extend inward at right angles to the side of the glabella; the next pair is nearly opposite the front end of the palpebral lobe; the anterior furrows are short and extend obliquely inward subparallel to the front margin of the glabella. Occipital ring narrow at the sides, widening toward the center where it is marked by a small sharp node a little back of the transverse center. Free cheeks large and surmounted on the inner side by a narrow eye lobe. The facial sutures cut the posterior margin a little within the genal angle and extend obliquely inward and slightly forward to the base of the eye lobes; curving over and around the eye lobes, they extend forward and downward, cutting the front margin on a line with the posterior base of the eye lobe. Number of thoracic segments unknown. Single specimens of the segments show that the axial lobe was nearly as wide as the pleural lobes, that it was moderately convex, and that a small node occurs at the center of each segment near the posterior margin; also that on the outer side of each segment a rounded transverse node is outlined from the main body of the segment by a slightly oblique transverse furrow; pleural lobes nearly flat out to the geniculation where they curve gently downward; each pleura has a furrow that is broad at its inner end next to the axial lobe and gradually narrows to the geniculation, where it terminates within the somewhat broadly rounded outer extremity; in well-preserved specimens a rounded ridge starts near the inner end of the pleural furrow and extends outward one-fourth of the length of the furrow.

The associated pygidia are semicircular, with the anterior margin almost transverse in the compressed specimens. The axial lobe is large and quite distinctly marked; it is divided by three transverse furrows into three rings and a terminal section that ends just within the outer border; a small node occurs near the posterior margin at the center of each ring; five anchylosed segments are outlined on the pleural lobes by furrows that progressively curve more and more backward from the first to the posterior one which adjoins the terminal segment; the furrows all terminate within the narrow, slightly flattened border.