. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. WHITTINGTON : ORDOVICIAN TRILOBITES 417 The next smallest cranidium comparable to the original of Plate 10, fifjures 1-4, is the original of Plate 10, figures 5-7, mm. in length (sag.). The anterior part of the glabella has the same inverted 'V outline in dorsal view and is more strongly raised, coming up to a blunt point in the mid-line at the base of the glabellar tongue; between the median part of the palpebral lobes the glabella is much narrower, the sides diverging forwards; a short basal glabellar furrow op
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. WHITTINGTON : ORDOVICIAN TRILOBITES 417 The next smallest cranidium comparable to the original of Plate 10, fifjures 1-4, is the original of Plate 10, figures 5-7, mm. in length (sag.). The anterior part of the glabella has the same inverted 'V outline in dorsal view and is more strongly raised, coming up to a blunt point in the mid-line at the base of the glabellar tongue; between the median part of the palpebral lobes the glabella is much narrower, the sides diverging forwards; a short basal glabellar furrow opposite the posterior part of the palpebral lobe, a longer median furrow opposite the middle part of the palpebral lobe — comparable positions to those of the. Fig:iue (). Bcmoplcurides Outline reconstructions of degree 0 individual, lacking free cheeks and hypostome. A, right lateral, B, oblique views, X 30. Abbreviations: a, anterior cephalic spine; mi, median tubercle of glabella; or, occipital ring; t, tubercle. Based on origi- nals of Plate 10, figures 8-14, 16, 17. furrows in larger glabellae. The palpebral lobe is subsemicircu- lar in outine, horizontal, and with a faint rim. It seems reasonable to suggest that the preceding stage of the cranidium (believed to be degree 0 by analogy with R. caelatus) is that shown in Plate 10, figures 8-11, 13 (cf. Text-fig. 6) with the striking large median glabellar tubercle situated opposite the anterior end of the palpebral lobes. The occipital ring is relatively narrow, the glabella straight-sided and expanding for- ward : two pairs of smooth areas are the lateral glabellar Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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