476 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Canada show the characteristic Mimella pedicle muscle scars and some details 
of the pallial marks. In the pedicle valve the ovarian impressions are small but 
prominent and marked by oblique wavy lines. The pallial trunks are separated 
by shallow depressions. In the brachial valve the main trunks are given off from 
the anterior ends of the adductors and branch anteriorly. 
MIMELLA INTERMEDIA Cooper, new species 
Plate 90, B, figures 16-20; plate o1, F, figure 25; plate o1, F, figures 26-28; 
plate 91,1, figures 37-39 
About medium in size for the genus, slightly wider than long with the great- 
est width at or slightly anterior to the middle ; cardinal extremities obtusely angu- 
lar; sides slightly sinuate just anterior to the cardinal extremity ; anterolateral 
extremities narrowly rounded; anterior margin truncated to emarginate; an- 
terior commissure rectimarginate. Costellae numbering 9 to II in 5 mm. at the 
anterior margin, separated by striae narrower than the costellae. 
Pedicle valve gently convex in lateral profile, the greatest convexity in the 
umbonal region and the anterior half or more somewhat flattened. Anterior pro- 
file broadly and gently convex but with short, steep lateral slopes. Beak some- 
what elongated ; umbo swollen ; median half occupied by a narrow, shallow sulcus 
which disappears at the margin. Flanks bounding sulcus gently swollen; pos- 
terolateral slopes short and steep. Interarea approximately procline, slightly 
curved but with the beak abruptly curved. Interior with large, heart-shaped 
muscle area; adductor track wide and anteriorly elevated; pallial marks not 
preserved. 
Brachial valve strongly convex, with the greatest curvature in the umbonal 
region; anterior half moderately convex; anterior profile strongly convex with 
long and steep lateral slopes; umbo sulcate; umbo strongly swollen; median part 
of anterior and middle flattened to faintly sulcate; flanks bounding median re- 
gion moderately swollen; posterolateral slopes steep; cardinal extremities de- 
flected to form small ears. Interior with thin cardinal process; notothyrial cavity 
moderately deep, median ridge narrow, not reaching to the middle. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Holoty pesos sh oBRiie oy aioe dla 15.2 15.2 17.6 14.8 12.0 
Paratype (1170449) oie 2s. esis 16.2 16.0 17.4 13.5 rie hi 
Types.—Holotype: 117044b; figured paratypes: 110703a,b, 117043, 117998; 
unfigured paratype: 1170442. 
Horizon and locality—Whistle Creek formation in Virginia: On Whistle 
Creek, 14 miles northwest of Lexington; on U. S. Highway 60 about 100 yards 
southeast of Whistle Creek, 2 miles northwest of Lexington, Lexington (15’) 
Quadrangle; 35 miles southwest of Bolton, Bristol (30’) Quadrangle. 
Elway formation in Tennessee: Along the road over Marble Bluff just north 
of summit about 8 miles west-northwest of Loudon, Loudon (30’) Quadrangle ; 
