. The Cyathaspididae; a family of Silurian and Devonian jawless vertebrates. Cyathaspididae. DENISON: THE CYATHASPIDIDAE 419 veloped. The orbits are placed anteriorly, and a pineal macula ap- pears to be absent. The dentine ridges of the central epitegum are longitudinal or somewhat sinuous. On the lateral epitegum a few. Fig. 143. Americaspis sp., dorsal shield and anterior half of ventral shield, CNHM, PF834 (X 1). (4-7) ridges are parallel to the edge, while behind the orbits the others are diagonal anteriorly and longitudinal posteriorly. The post- rostral area is probably not distinct; th
. The Cyathaspididae; a family of Silurian and Devonian jawless vertebrates. Cyathaspididae. DENISON: THE CYATHASPIDIDAE 419 veloped. The orbits are placed anteriorly, and a pineal macula ap- pears to be absent. The dentine ridges of the central epitegum are longitudinal or somewhat sinuous. On the lateral epitegum a few. Fig. 143. Americaspis sp., dorsal shield and anterior half of ventral shield, CNHM, PF834 (X 1). (4-7) ridges are parallel to the edge, while behind the orbits the others are diagonal anteriorly and longitudinal posteriorly. The post- rostral area is probably not distinct; the ridges of the postrostral area are continuous with those of the central epitegum, and perhaps in some cases with those of the rostral epitegum. The ridge pattern of the rostral epitegum is extremely variable; usually there are 3-5 broad, flat ridges parallel to the anterior edge; behind these the ridges may be longitudinal (PF 862, 866), or denticulate anteriorly and longitudinal posteriorly (PF865a), or all denticulate (PF3641), or in one case mostly transverse (PF 865b). New York State Mus. 10678 (fig. 142), the anterior part of a dor- sal shield from the same locality, is doubtfully referred to this species. On the rostral epitegum there are almost no ridges parallel to the anterior edge, and most of the rostral ridges radiate sinuously. This specimen has been identified as Cyathaspis "wardelli" by Flower and Wayland-Smith (1952, pi. 2, fig. 4) and by Kilfoyle (1959, p. 108). Americaspis sp. CNHM, PF833 and 834, from the Late Silurian, Landisburg sandstone, % mile north-northwest of Landisburg, Perry County, Pennsylvania, were originally one block of sandstone containing six. 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 Denison, Robert H. (Robert Howland), 1911-1985; Chicago Natural History
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