940 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
way 25E, 4 mile north of Indian Creek, Howard Quarter (T.V.A. 162-NW) 
Quadrangle; west of Lone Mountain, Tazewell (T.V.A. 154-NE) Quadrangle. 
Wardell formation in Virginia: On Fugates Hill north of Mendota, Bristol 
(30) Quadrangle. 
Ridley= Wardell formation in Georgia: On U. S. Highway 27 just north of 
its crossing over Chickamauga Creek, Kensington (T.V.A. 206-SE) Quadrangle. 
Carters formation (Oxoplecia bed) in Alabama: Quarry 0.3 mile north of 
Gate City, Leeds (15’) Quadrangle. 
Mahan formation in Tennessee: 2 miles southeast of Snow Hill, Snow Hill 
(T.V.A. 112-NE) Quadrangle. 
STROPHOMENA MAGNA Wilson 
Strophomena magna Witson, Trans. Roy. Soc. Canada, ser. 3, vol. 39, sec. 4, p. 134, pl. 1, 
figs. 13, 14, 1945; Geol. Surv. Canada, Bull. 8, p. 104, pl. 9, figs. 11, 12, 1946. 
Type.—Holotype: G.S.C. 7579. 
Horizon and locality—Rockland formation in Ontario, Canada: At Stewart 
Quarry, Rockland. 
STROPHOMENA MEDIALIS Butts 
Plate 259, A, figures 1-16 
Strophomena medialis Butts, Virginia Geol. Surv. Bull. 52, pl. 87, figs. 1-6, 1942. 
Large and thick, wider than long with the hinge forming the widest part; 
cardinal extremities alate; front margin broadly rounded; lateral margins usu- 
ally oblique. Surface multicostellate with the larger costellae separated by 1 to 
4 finer ones. All costellae enlarging anteriorly with the result that difference in 
size between primary and subsequent costellae is greatly lessened; 13 to 15 
costellae occupy 5 mm. at the front margin of an adult. 
Pedicle valve moderately to deeply concave with depressed part of valve oc- 
cupying most of the surface. Cardinal extremities strongly deflected toward the 
brachial valve ; surface of cardinal extremities flat to moderately concave. Um- 
bonal region gently convex with the convexity continued anteriorly as a low 
fold for one-third to one-half the length of the valve. Interarea long and promi- 
nent, strongly apsacline; pseudodeltidium low, subcarinate. 
Brachial valve moderately convex with the greatest convexity located slightly 
anterior to the middle. Posterior slope moderately steep, gently convex in pro- 
file ; anterior slope somewhat steeper than the posterior one and also gently con- 
vex in profile. Median sulcus shallow but prominent, having about the same 
relation to the brachial valve that the fold of the pedicle valve has to that valve. 
Region about the sulcus gently swollen, with gentle to moderately steep slopes 
to the depressions setting off the deflected cardinal extremities, these depressions 
varying from gently to deeply concave. Lateral slopes moderately steep. Inter- 
area exceedingly short, the palintrope forming a narrow ridge along the line 
of valve juncture. Chilidium short and low. 
Interior of pedicle valve with a nearly circular to broadly cordate muscle area 
having a diameter equal to about one-third the valve length. Median ridge in- 
