. Bulletins of American paleontology. 16 Bulletin 153 322 Stratigraphic position.—Briones formation, lower upper Miocene, in a moderately well cemented buff sandstone. Remarks.—Because of the numerous ribs, this species and C. pris- finum Keen, n. sp. have been confused by authors with the Recent Tra- chycardiiim {Dallocardia) quadragenarium, a form that has well-de- \eloped spinose ribs on the posterior slope and a relatively short, straight hinge. In outline, number of ribs, and degree of ventricosity this new species agrees well with the Recent C. blandum (Gould) but differs in being consid
. Bulletins of American paleontology. 16 Bulletin 153 322 Stratigraphic position.—Briones formation, lower upper Miocene, in a moderately well cemented buff sandstone. Remarks.—Because of the numerous ribs, this species and C. pris- finum Keen, n. sp. have been confused by authors with the Recent Tra- chycardiiim {Dallocardia) quadragenarium, a form that has well-de- \eloped spinose ribs on the posterior slope and a relatively short, straight hinge. In outline, number of ribs, and degree of ventricosity this new species agrees well with the Recent C. blandum (Gould) but differs in being considerably larger, an average C. blanduTu having a height of about 25 mm. It is one of the earliest, if not the earliest, spe- cies of Clinocardium. Another Briones form, tentatively assigned by Trask (Univ. Calif. Publ., Bull. Dept. Geol. Sci., vol. 13, p. 150, pi. 5, fig. 3, 1922) to "Cardium corbis (Martj^n), n. ;, is probably Tra- chycardium scliencki (Wiedey), 1928, as recognized by Wiedey in 1929 in an unpublished Stanford University thesis but overlooked by Keen and Bentson in the "Check List of California Tertiary Marine Mol- lusca" (Geol. Soc. Amer., Spec. Paper 56, p. 33, 1944). Clinocardium pristinum Keen, n. sp. PI. 1, figs. 9, 15; text figs. 7, 8 fCardium (Cerastodcrma) cf. corbis (Martyn), Etherington, 1931, Univ. California Publ. Bull. Dept. Geol. Sci., vol. 20, p. 77, 5, fig. 11. Astoria formation, southwestern Washington, 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. Ithaca, N. Y. , Paleontological Research Institution [etc. ]
Size: 2411px × 1037px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorpaleontologicalresearchinstitutionit, bookcentury1900
