. Bulletins of American paleontology. 438 Bulletin 238 ooq'qo Text-figure 54.—Transverse serial sections of Dielasma sp. X2, USNM 154942 from USNM locality 9048, measurements (mm) from ventral beak. Beecheria chouteauensis (Weller) 1914 PI. 45, figs. 8a-e; Text-fig. 55 Illinois Geol. Sur., Mon. 1, p. 257, pi. Dielasma chouteauensis Wei 32, figs. 1-17, text-fig. 29. 1937. (Non) Dielasma chouteauensis Weller, Nalivkin, Tsentral. nauch. Geol. Inst., Trudy, vol. 99, p. 128, pi. 32, fig. 3; pi. 34, figs. 1, 2. 1938. Dielasma chouteauensis Weller, Branson, Univ. Miss
. Bulletins of American paleontology. 438 Bulletin 238 ooq'qo Text-figure 54.—Transverse serial sections of Dielasma sp. X2, USNM 154942 from USNM locality 9048, measurements (mm) from ventral beak. Beecheria chouteauensis (Weller) 1914 PI. 45, figs. 8a-e; Text-fig. 55 Illinois Geol. Sur., Mon. 1, p. 257, pi. Dielasma chouteauensis Wei 32, figs. 1-17, text-fig. 29. 1937. (Non) Dielasma chouteauensis Weller, Nalivkin, Tsentral. nauch. Geol. Inst., Trudy, vol. 99, p. 128, pi. 32, fig. 3; pi. 34, figs. 1, 2. 1938. Dielasma chouteauensis Weller, Branson, Univ. Missouri Studies, vol. 13, No. 3, p. 55, pi. 5, figs. 28-30. 1956. ( ?) Dielasma chouteauensis Weller, Simorin, Akad. Nauk Kazakhstan SSR, p. 256, pi. 26, figs. 13-20. 1958. Dielasma chouteauensis Weller, Armstrong, New Mexico Bur. Mines Min. Res., Mem. 5, pp. 26, 27, pi. 2, figs. 1-7, 11-14, 17-28, 31. 1962. Beecheria cf. B. chouteauensis (Weller), Armstrong, New Mexico Bur. Mines Min. Res., Mem. 8, p. 63, pi. 9, fig. 20. Types.—Weller (1914, p. 257) did not designate a holotype. His suite of syntypes are in the Univ. Chicago Walker Museum collec- tions, numbers 12237, 9703, 9666, and 8547. (Now in the Field Natu- ral History Museum.) Distinguishing characters.—This species is characterized by its subequally biconvex moderately compressed valves, subovate out- line, evenly convex surfaces, rectimarginate anterior commissure, rounded front margin, and faintly costellate prosopon; internally the inner hinge plates unite posteriorly and rise slightly off the floor of the valve. Measurements (mm.) nf illustrated specimen.—USNM No. 154943. Length ; width ; thickness 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 Paleontological Research Institution (Ithaca, N. Y. ); Columbia University. Ithac
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