598 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Ward Cove formation in Tennessee: 2 miles southwest of Hall Crossroad, 
Fountain City (T.V.A. 146-SW) Quadrangle. 
Sevier formation in Tennessee: + mile northeast of Miser, Louisville (T.V.A. 
138-SE) Quadrangle. 
Discussion.—This species can be recognized by its fairly large size, obtuse and 
elevated beak, narrowly rounded anterolateral extremities and numerously cos- 
tated flanks. It differs from P. costata in the latter character as well as in size 
and form. 
PLECTOCAMARA COSTATA Cooper, new species 
Plate 122, B, figures 9-21; plate 123, E, figures 22-26; plate 123, F, figures 27-31; 
plate 138, F, figures 40-42 
Shell small, subpentagonal in outline; posterolateral margins straight forming 
an angle of about 120°. Sides narrowly rounded; anterior margin subtruncated ; 
anterior commissure strongly uniplicate ; surface costate, fold marked by 3 costae, 
sulcus containing 2 costae, and flanks marked by 4 costae. 
Pedicle valve slightly convex in lateral profile; broadly convex in anterior 
profile but depressed medianly ; umbo smooth; sulcus originating about 1 mm. 
anterior to the beak, deepening rapidly and forming a moderately long, narrow 
tongue. Flanks depressed convex, with gentle slopes. . 
Brachial valve deeper than the pedicle one and moderately convex in lateral 
profile; strongly convex in anterior profile. Fold originating on the umbo, 
strongly elevated at the front and with steep sides. Flanks rounded and with 
steep slopes depressed below the fold. Interior with sessile cruralium. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
FIGIOEY PE 44 ¢ystee ssldbn > 5.5 5.2 6.6 1.5 3.9 
Paratype (111368a) .... 4.6 4.2 4.9 1.0 1.9 
Types——Holotype: 111360a; figured paratypes: 111356, 111368a,b, 117184, 
117943a,b; figured specimen: 123457; unfigured paratype: 117184b. 
Horizon and locality.—Lincolnshire formation (Hogskin member) in Tennes- 
see: 3 and 44 miles west-southwest of Thorn Hill; 0.4 mile east-northeast of Red 
Hill; $ mile north of Thorn Hill on U. S. Highway 25E; Avondale (T.V.A. 
162-SW ) Quadrangle; 1 mile southwest of Washburn, Dutch Valley, (T.V.A. 
154-SE) Quadrangle; 4 mile north of Eidson, Kyles Ford (T.V.A. 170-SE) 
Quadrangle ; 4 mile north of Rose Hill, Maynardville (T.V.A. 145-SE) Quad- 
rangle; 4 mile southwest of Fleanor Mill, Powell Station (T.V.A. 137-SE) 
Quadrangle; Evans Ferry section, north of Indian Creek, Howard Quarter 
(T.V.A. 162-NW) Quadrangle; 2 miles southwest and 1.7 miles northwest of 
Hall Crossroad, Fountain City (T.V.A. 146-SW) Quadrangle. 
Lincolnshire formation in Virginia: Quarry at Marcem, 2 miles west of Gate 
City, Gate City (T.V.A. 188-SE) Quadrangle. 
Ward Cove formation in Tennessee: ? mile southeast of Mount Eager Church, 
Powder Springs (T.V.A. 154-SW) Quadrangle. 
