. Carnegie Institution of Washington publication. 202 FOSSIL TURTLES OF NORTH AMERICA. A wholly similar humerus is contained in a small collection of hones sent the writer from the University of Chicago. The few skeletal hones accompanying it are not sufficient to identify the humerus as that of P. advena, but it seems probable that both it and the humerus in the American Museum belong here. Genus ARCHELON Wieland. Premaxillary beak more strongly developt than in Protostega. Crushing-surface of upper jaw mostly on the premaxillaries; that on the maxillae extending back only to opposite the cho
. Carnegie Institution of Washington publication. 202 FOSSIL TURTLES OF NORTH AMERICA. A wholly similar humerus is contained in a small collection of hones sent the writer from the University of Chicago. The few skeletal hones accompanying it are not sufficient to identify the humerus as that of P. advena, but it seems probable that both it and the humerus in the American Museum belong here. Genus ARCHELON Wieland. Premaxillary beak more strongly developt than in Protostega. Crushing-surface of upper jaw mostly on the premaxillaries; that on the maxillae extending back only to opposite the choanae. Lower jaw with the rami not co-ossified at symphysis; at least, not until old age. Entoplastron T-shaped, with the anterior border concave from end to end. Radial process of humerus feeble. Type: Archelon ischyros Fig. 260.—Archelon ischyros. Carapace with the entoplastron. XjTS. Archelon ischyros Wieland. Figs. 260-268. Archelon ischyros, WlELAND, Amer. [our. Sci. (4), II, 1896, p. 399, plate vi, text-figs. 2-19; ibid., IX, 1900, p. 237, plate ii, text-figs. 1-3, 6; ibid., XIV, 1902, p. 99, fig. 2; ibid., XV, 1905, p. 211, fig. I; Ann. Carnegie Mus., iv, 1906 (1907), p. 8, figs. 1, 4.—Hay, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 440. Protostega ischyros, WlLLISTON, Univ. Geol. Surv. Kansas, II, 1897, p. 246.—Wieland, Amer. Jour. Sci. (4), v, 1898, p. 15, plate ii, text-figs. 1, 2. We owe our knowledge of this species to the study and the publications of Dr. G. R. Wieland. All the known specimens have been found by him near the South Fork of Cheyenne River in South Dakota, in the upper beds of that part of the Pierre formation that is below. 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 Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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