. The Cyathaspididae; a family of Silurian and Devonian jawless vertebrates. Cyathaspididae. 360 FIELDIANA: GEOLOGY, VOLUME 13 orbital part (fig. 111). The latter is to be identified as the anterior end with curved ridges of the plates labeled b and b' in Matthew's -:'â rCP v % â â -- . lepi. ,lep, Fig. 111. Cyathaspis acadica, type, parts of dorsal and ventral shields; Royal Ontario Museum 1117 (X 5/2). cep, central epitegum; lep, lateral epitegum; rep, rostral epitegum; vs, ventral shield. figure (1888, pi. 4, fig. 4). In its known characters there is nothing to distinguish this species from
. The Cyathaspididae; a family of Silurian and Devonian jawless vertebrates. Cyathaspididae. 360 FIELDIANA: GEOLOGY, VOLUME 13 orbital part (fig. 111). The latter is to be identified as the anterior end with curved ridges of the plates labeled b and b' in Matthew's -:'â rCP v % â â -- . lepi. ,lep, Fig. 111. Cyathaspis acadica, type, parts of dorsal and ventral shields; Royal Ontario Museum 1117 (X 5/2). cep, central epitegum; lep, lateral epitegum; rep, rostral epitegum; vs, ventral shield. figure (1888, pi. 4, fig. 4). In its known characters there is nothing to distinguish this species from Cyathaspis and very little to distin- guish it from C. banksi. The type of ornamentation is precisely the same, with round-topped dentine ridges of two sizes on the central parts of the dorsal and ventral shields (fig. 159,A) and of uniform size elsewhere. The pattern of the ridges is similar also. The pat- tern of the postrostral field has not been described in Cyathaspis banksi; in C. acadica the pineal macula is marked by circular ridges around a tubercle (Matthew, 1888, pi. 4, fig. 2), and in front of it ridges radiate toward the rostral epitegum. The ventral shield is surrounded anteriorly and laterally by a band of uniform-sized ridges; Matthew (1888, p. 51) described an anterior triangular area of irreg- ular ridges on it, comparable to the postrostral field of the dorsal shield; this area is not now preserved on the type nor is it recogniz- able on Matthew's figures. It is possible that the fragment e of Matthew's figure (1888, pi. 4, fig. 1) represents part of a branchial plate; this part of the type is no longer preserved. The shape, pro- portions, and size of C. acadica cannot be accurately determined from material available at 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,
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