. Bulletins of American paleontology. . B Text-figure 6. Cardinalia of Wilberrya fragilis showing character of tooth processes and crural bases. A — ventral valve, B — dorsal valve. Drawn from specimens shown in fig. 8, Plate 5, and fig. 13-14, Plate 5. species most similar to Wilberrya. Furthermore, there is a progres- sive reduction of the crural bases in Crurithyris approaching the condition found in Wilberrya. These morphologic progressions indi- cate that Wilberrya is a direct descendant of Crurithyris. Wilberrya is uncommon in the biotas in which it is found. It oc- curs in predominantly
. Bulletins of American paleontology. . B Text-figure 6. Cardinalia of Wilberrya fragilis showing character of tooth processes and crural bases. A — ventral valve, B — dorsal valve. Drawn from specimens shown in fig. 8, Plate 5, and fig. 13-14, Plate 5. species most similar to Wilberrya. Furthermore, there is a progres- sive reduction of the crural bases in Crurithyris approaching the condition found in Wilberrya. These morphologic progressions indi- cate that Wilberrya is a direct descendant of Crurithyris. Wilberrya is uncommon in the biotas in which it is found. It oc- curs in predominantly moUuscan faunas in the Arcturus Group, and appears to have been tolerant of nearshore environmental conditions (periodic high turbidity and high energy). Brabb and Grant (1971) illustrated a larger unnamed species of this genus (listed as Martinia sp. undet.) from the Tahkandit Formation of Alaska which contains an arctic type fauna. Gobbett (1963) and Bamber and Waterhouse (1971) illustrated specimens of "Martinia ; which may well be- long in this genus, but the internal features of these forms are not known. Etymology. — Named for W. B. N. Berry, of the Dept. of Paleontology, University of California, Berkeley. Wilberrya fragilis, n. sp. PI. 5, figs. 8-19 Description. — Ventral valve: Small, thin-shelled, wider than long, with greatest width just anterior to the hingeline; hingeline short; valve well-inflated, with slight fold and sulcus developed and a broad low fold on each lateral slope at maturity; beak overhang- ing, not prominent, and strongly incurved; interarea low, containing an open delthyrium bounded by low ridges which project as tooth. 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.
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