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Show APPENDIX B.- PALEONTOLOGY. 409 B R A C H I O P O D A . TSKKBRATULA 8UBTILITA. PLATB II. Fio. 1 ab, 2 ab. Gibbous, obovoid; valves nearly equal, convex; beak of the dorsal valve elevated, incurved, and perforated at the apex; a mesial depression commencing just below the centre and extending to the front, which is produced and elevated, filling a broad sinus in the ventral valve; surface marked by strong concentric striae, or lines of growth, with faint, often almost imperceptible radiating striae. Fig. 1 a, a young individual. Fig. 1 b, an individual of the ordinary size and form. Fig. 2 a, a more gibbous form. Fig. 2 b, profile view of the preceding. Fig. 2 c, front view of the same. Loc. Missouri River, near Weston. SPIRIFER HEMIPLICATA. ^ 2fv/ T\' j ( PLATB II. Fio. 8ab. Shell gibbous; ventfal valve more elevated, beaks nearly equal; entire surface marked by finely radiating strata; each valve with about three plications on each side of the mesial sinus and elevation, which plications extend halfway from the base to the beak, leaving the upper half of the shell marked only by fine striae; anterior portion of the dorsal valve produced in a long extension, which fills a deep angular sinus in the ventral valve. Fig. 3 a, view of the dorsal valve, which, from distortion, shows the beak of the ventral valve projecting above it. Fig. 3 b, front view of the same specimen. • • Loc. Missouri River, near Weston. SPIRIFER OCTOPLICATA? ' l\ / i***. > |