656 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
proximately 90°. Sulcus marked by 4 to 6 narrowly rounded, slender costae, 
fold marked by 5 to 7 costae, and the flanks by 7 or 8 costae. 
Pedicle valve unevenly and gently convex in lateral profile, the most convex 
part located just anterior to the umbo; anterior profile broadly convex and with 
the median region slightly depressed. Beak strongly incurved and overhanging 
the umbo of the brachial valve. Umbo moderately swollen; sulcus originating 
just posterior to the middle or about 5 mm. anterior to the beak. Sulcus mod- 
erately deep; tongue short, not geniculated. Flanks flat, moderately sloping. 
Brachial valve deeper than the pedicle valve, moderately convex in lateral pro- 
file, moderately strongly arched in anterior profile. Umbo strongly swollen, 
marked medially by a shallow and narrow sulcus. Fold becoming defined near 
the middle, not strongly elevated at any point on its length. Flanks rounded and 
moderately steep. 
Measurements in mm.— 
Brachial 
Length length Width Thickness 
BIDIOLY PE |. Soe vicecc os HOE ate ote Se 11.8 10.7 12.9 72 
Paratype eee sie ee ate 17 10.3 10.6 8.9 
Types.—Holotype: 117234a; figured paratype: 117234b. 
Horizon and locality—Aylmer formation (Rockcliffe member) in Ontario, 
Canada: 2 miles south of Rockland. 
Discussion.—This species has been commonly referred to R. plena in the re- 
gion around Ottawa. In appearance R. wilsonae is suggestive of that species but 
does not attain its large size or great depth. R. plena of the same size as R. wil- 
sonae is much deeper, has a shallower sulcus and a more triangular shape than 
the Ottawa species. The deeper varieties of R. wilsonae compared with speci- 
mens of FR. plena of the same length have a deeper sulcus. 
ROSTRICELLULA sp. 1 
Plate 137, G, figures 47-52 
Small, length and width nearly equal; fold marked by 3 costae, the sulcus by 
2. Flanks marked by 5 or 6 costae. Valves subequal in depth; sulcus originat- 
ing near the middle ; fold low; tongue short. 
Measurements in mm.—Figured specimen, length 6.2, brachial length 5.5, 
width 6.4, thickness 4.8. 
Figured specimen.—117236. 
Horizon and locality—Bromide formation (Pooleville member—bed E of 
Cooper) in Oklahoma: On Spring Creek, sec. 17, T. 2 S., R. 1 W., Murray 
County. 
Discussion.—A single specimen was found in this bed of the Bromide, and 
no other members of the genus were taken from that part of the column. The 
present specimen, in its thickened shell and strongly marked interrupted growth 
stages, is obviously not a normal specimen. Abnormality is further emphasized 
by the presence of a bifurcated costa which is exceptional in this genus of 
rhynchonellids. 
