22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
Pedicle valve with uneven lateral profile, flattened in the umbonal 
region, but gently convex in the anterior region; anterior profile 
broadly convex but with steep lateral margins. Interarea moderately 
long, triangular ; pseudodeltidium narrow and strongly convex ; palin- 
trope steeply apsacline. Sides of interarea forming an angle of about 
110°. Median septum, short, off-center. 
Brachial valve evenly and moderately convex in lateral profile; 
anterior profile broadly convex but with a narrow median depression. 
Lateral slopes moderately steep. Umbo somewhat swollen; sulcus 
originating at the beak narrow and shallow to the front margin. 
Cardinal process moderately long. 
Types.—Figured specimens, U.S.N.M. 125312, 125315. 
Localities —S68, S101; U.O. 2204-3. 
Discussion——The specimens assigned here are poorly preserved. 
They suggest an undescribed species from the upper Leonard of the 
Glass Mountains, Texas, but may be the young of Derbyia sp. 1 above. 
MEEKELLA sp. 1 
Plate 1D, figure 9 
This genus is represented by a single specimen broken nearly 
through the middle but preserving the dental plates and most of the 
pseudodeltidium. The specimen represents a small species about 19 
mm. long, about the same in width, and having a thickness of about 
18 mm. Width of hinge 15 mm. The beak is erect and the interarea 
shows only slight curvature. The surface was marked by about 14 
plications. The brachial valve is thickest posteriorly, and its beak 
is strongly incurved as is usual in the genus. 
Type.—Figured specimen, U.S.N.M. 125313. 
Locality.— 637. 
Discussion.—None of the Russian meekellas is like this one. Meek- 
ella eximia (Eichwald) is larger and more strongly plicated; Meek- 
ella uncitoides Tschernyschew is not strongly plicated and is a much 
more elongated species. Specimens figured by Tschernyschew (1902, 
pl. 24, figs. 7a,b) as M. striatocostata (Cox) are suggestive but the 
ribbing is more subdued. None of the Alpine species described by 
Schellwien (1900) even remotely resembles the Oregon species. 
Compared to American Permian species the Oregon form is most 
like M. striatocostata, M. difficilis Girty, and M. skenoides Girty. 
These species are small compared with the generality of American 
meekellas. The ribbing of M. difficilis is similar to that of the Oregon 
species but is not so sharp and strongly elevated. Furthermore the 
