| OCR Text |
Show 1891.] LERMAL PLATES OF HOMOSTEUS. 199 gradually diminish to the anterior third of the bone and then pass into broad undulations bounding a median longitudinal hollowr. Posteriorly, where the two lateral occipitals approach most closely, the ridge is an arrowhead-shaped boss, the apex directed backwards and the base forwards ; and at this point there may have been a descending plate of bone. At its bifurcation the ridge Figs. 1-4. Dermal plates of Homosteus milleri, from the Caithness Flagstones; all shown from the visceral aspect, of one quarter the natural size. 1, median occipital; 2, left lateral occipital; 3, anterior median ventral; 4, impression of left anterior ventro-lateral. J, facettes for overlap. becomes m u c h less elevated, broader and rounder, gradually diminishing forwards as just described ; and on either side is a series of shallow, transverse linear grooves, symmetrically disposed in several |
