. The Cyathaspididae; a family of Silurian and Devonian jawless vertebrates. Cyathaspididae. DENISON: THE CYATHASPIDIDAE 345 Archegonaspis Integra, fig. 202, a drawing. Shows k2-k9. Protopteraspis primaeva, fig. 197B, a drawing. Shows k2-k9f but photographs, figs. 197A and 199A, show only k2~ks. Fig. 106. Poraspis cylindrica; dorsal shield preserved largely as an internal impression and showing molds of gill pouches, pineal fossa, semicir- cular canals and cranial cavity (from Kiaer, 1932). Type, Paleontologisk Museum, Oslo, D 205 ( X about 2).. It will be noted that no evidence is presented f
. The Cyathaspididae; a family of Silurian and Devonian jawless vertebrates. Cyathaspididae. DENISON: THE CYATHASPIDIDAE 345 Archegonaspis Integra, fig. 202, a drawing. Shows k2-k9. Protopteraspis primaeva, fig. 197B, a drawing. Shows k2-k9f but photographs, figs. 197A and 199A, show only k2~ks. Fig. 106. Poraspis cylindrica; dorsal shield preserved largely as an internal impression and showing molds of gill pouches, pineal fossa, semicir- cular canals and cranial cavity (from Kiaer, 1932). Type, Paleontologisk Museum, Oslo, D 205 ( X about 2).. It will be noted that no evidence is presented for more than seven pairs of gills (that is, k2-ks). Precisely the same seven pairs are present in "Archegonaspis" drummondi (fig. 156), Listraspis canaden- sis (fig. 132,A), Vernonaspis sekwiae, V. vaningeni, and Anglaspis expatriata (fig. 151,A). Only six can be seen in Allocryptaspis ellip- tica (Bryant, 1935, fig. 1, and pi. 5), and in Homalaspidella niiida (see p. 344). The seventh gill (k8 of Stensio) lies just in advance of of the external branchial opening, and it is probable that there were no gills behind it, and no posterior branchial ducts or other related structures inferred by Stensio (1958, pp. 393-394). The impressions of the gills on the dorsal and ventral shields in- dicate that the gill chambers were transversely arranged, very high. 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
Size: 1105px × 2261px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorchicagonaturalhistorymuseum, bookcentury1900, bookcoll
