. The Cyathaspididae; a family of Silurian and Devonian jawless vertebrates. Cyathaspididae. 386 FIELDIANA: GEOLOGY, VOLUME 13 ro -. ro — • popi ' H ?'(r'' orb ra Is *& if B Fig. 126. Pionaspis planicosta, type; incomplete dorsal shield, National Mu- seum of Canada 10035 (X 1). A, dorsal view; B, lateral view of left side. bro, branchial opening; orb, orbit; pbl, postbranchial lobe; pop, preorbital process; ro, rostrum. orbital ratio is about .14. The ridge pattern of the central epitegum, including the postrostral field, and of the ventral shield, is semi- elliptical, with the ridges conv
. The Cyathaspididae; a family of Silurian and Devonian jawless vertebrates. Cyathaspididae. 386 FIELDIANA: GEOLOGY, VOLUME 13 ro -. ro — • popi ' H ?'(r'' orb ra Is *& if B Fig. 126. Pionaspis planicosta, type; incomplete dorsal shield, National Mu- seum of Canada 10035 (X 1). A, dorsal view; B, lateral view of left side. bro, branchial opening; orb, orbit; pbl, postbranchial lobe; pop, preorbital process; ro, rostrum. orbital ratio is about .14. The ridge pattern of the central epitegum, including the postrostral field, and of the ventral shield, is semi- elliptical, with the ridges converging only slightly posteriorly, but converging strongly anteriorly to form a continuous curve around the anterior end. Pionaspis planicosta, new species. Figures 126-128. Type.—National Museum of Canada, 10035, incomplete dorsal shield (figs. 126-127). Referred specimen.—CNHM, PF 3681, ventral shield (fig. 128). Occurrence.—Early Devonian, about 30 miles northwest of Mun- cho Lake, British Columbia, 59° 07' 30" N.; 126° 22'W. (locality R5-61, 2100' of California Standard Company). Diagnosis.—The length of the dorsal shield is 77 mm., and of the ventral shield is about 65 mm. The width ratio of the dorsal shield is .62. On the dorsal shield there are 53^-6 dentine ridges per milli- meter, and they are flat-topped, except that laterally and postero-. 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 Museum. Chicago : Chicago Natural History Museum Press
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