482 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Pedicle valve unevenly convex in lateral profile with the posterior half mod- 
erately convex and the anterior half depressed toward the brachial valve. An- 
terior profile broadly and gently convex, the median region forming the crest of 
the arch. Beak erect and only slightly incurved ; umbo somewhat narrowly swol- 
len ; posteromedian region gently swollen ; anteromedian area depressed to form a 
shallow sulcus; flanks bounding sulcus slightly swollen ; lateral slopes gentle but 
steepening toward the cardinal extremities. Interarea moderately long, nearly 
catacline. 
Brachial valve fairly evenly and moderately convex in lateral profile; anterior 
profile strongly convex with long and steep lateral slopes. Umbonal region nar- 
rowly convex and merging into the swollen median region. Fold not pronounced, 
defined as a broad swelling of the anterior ; lateral slopes long ; cardinal extremi- 
ties prominent. Interarea moderately long, curved over the pedicle interarea. 
Interior of pedicle valve with strongly elevated adductor track and long, nar- 
row diductor troughs. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Holotype !:. scistt ees 2h. . 12.9 13.0 16.0 13.0 7.8 
Paratype (117046b).......... 16.0 ? 19.6 15.3 ry 
+ (TT7OASA Ne a's dilcd: 14.3 13.5 17.0 127 8.6 
Types.—Holotype: 117046a; figured paratypes: 110737, 117046b, 1170474, 
117048a; unfigured paratypes: 117047b,c. 
Horizon and locahity—Lincolnshire formation (Hogskin member) in Tennes- 
see: 0.2 mile northwest up farm lane, 4 mile southwest of Fleanor Mill, Powell 
Station (T.V.A. 137-SE) Quadrangle; 500 feet below ‘‘Holston” marble, Lee 
Valley Post Office, Lee Valley (T.V.A. 171-NW) Quadrangle; 4 mile south- 
west of Beeler Cemetery, Hogskin Valley, Powder Springs (T.V.A. 154-SW) 
Quadrangle; 2 miles southwest of Hall Crossroad, northwest quarter center 
subquad., Fountain City (T.V.A. 146-SW) Quadrangle; Evans Ferry, Howard 
Quarter (T.V.A. 162-NW) Quadrangle; 1 mile southeast of Washburn, Dutch 
Valley (T.V.A. 154-SE) Quadrangle; 2.65 miles southwest of Mount Eager 
Church, Hogskin Valley, Powder Springs (T.V.A. 154-SW) Quadrangle; Red 
Hill, 44 miles southwest of Thorn Hill, Avondale (T.V.A. 162-SW) Quad- 
rangle; 3 and 33 miles west-southwest of Thorn Hill, Avondale (T.V.A. 
162-SW) Quadrangle; stream and road crossing on U. S. Highway 25E, 4 mile 
north of Thorn Hill, Avondale (T.V.A. 162-SW) Quadrangle; Raccoon Valley, 
5 miles south of Clinton, Powell Station (T.V.A. 137-SE) Quadrangle. 
Discussion.—This is a species of moderate size suggesting small examples of 
Mimella globosa. Confusion with the latter species is easy because the Hogskin 
shale has been called Ottosee, parts of which are the source yielding M. globosa. 
The two species may be distinguished by the smaller size of the Hogskin form 
which generally has prominent and slightly obtuse cardinal extremities, a some- 
what more convex and deeper pedicle valve, more strongly apsacline interarea. 
This species differs from M. twmida in its much smaller size and finer costellae. 
