. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palæontological science. Paleontology. THE UPPER SILURIAN PERIOD. 129 species of Platyostoma (fig. 72, h) also belong to the same family; and the entire group is continued throughout the Devonian into the Carboniferous. Amongst other well-known Upper Silurian Gasteropods are species of the genera Holopea. Fig. 72.—Upper Silurian Gasteropods. a, Platyceras ventrlcosum. Lower Helder- berg, America; b, Euonphalics discors, Wenlock, Britain ; c, Holopella obsoleta, Lud- low, Britain ; d, Platysc
. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palæontological science. Paleontology. THE UPPER SILURIAN PERIOD. 129 species of Platyostoma (fig. 72, h) also belong to the same family; and the entire group is continued throughout the Devonian into the Carboniferous. Amongst other well-known Upper Silurian Gasteropods are species of the genera Holopea. Fig. 72.—Upper Silurian Gasteropods. a, Platyceras ventrlcosum. Lower Helder- berg, America; b, Euonphalics discors, Wenlock, Britain ; c, Holopella obsoleta, Lud- low, Britain ; d, Platyschisvia helicites. Upper Ludlow, Britain ; e, Holopella grncilior, Wenlock, Britain ;_/, Platyceras multisinitatuni, Lower Helderberg, America; g. Hole- pea snbconica. Lower Helderberg, America; //, h', Platyostoma Niagarense, Niagara Group, America. (After Hall, M'Coy, and Salter.) (fig. 72, g), Holopella (fig. 72, c), Platyschisvia (fig. 72, d), Cyclonema, Pleiirotomaria, Murchisonia, Troc/ionema, &c. The oceanic Univalves {Hetej'opods) are rep- resented mainly by species of Bellero- phon; and the Winged Snails, or Ptero- pods, can still boast of the gigantic Theccd and Co7nilaricg, which characterise yet older deposits. The commonest genus of Pteropoda, however, is Teniaadites (fig. 73), which clearly belongs here, though it has commonly been regarded as the tube of an Ann elide. The shell in this group is a conical tube, usually adorned with prominent transverse rings, and often with finer transverse or longitudi- nal strife as well; and many beds of the Upper Silurian exhibit myriads of such tubes scattered promis- cuously over their surfaces. I Fig 73.— Tentaciiliiesor- iiatus. Upper Silurian of Europe and North 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 Nicholson, Henry Alleyne,
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Keywords: ., bookaut, bookcentury1800, bookdecade1870, booksubjectpaleontology
