428 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
FAGIOEO IS hn!s ates :5/0Pub ahce> mechs 14.2 13.5 17.5 15.7 5.2 
Paratype (UEOASS ac sins ms 22.2 22.4 28.3 22.6 8.8 
Types.—Holotype: 110474b; figured paratypes: 110433, I10474a,c,e; un- 
figured paratype: 110474d. 
Horizon and locality.—Lincolnshire formation (Hogskin member) in Tennes- 
see: In Evans Ferry section about 1 mile north of Indian Creek on U. S. High- 
way 25E, Howard Quarter (T.V.A. 162-NW) Quadrangle; 0.4 mile east- 
northeast of Red Hill, Avondale (T.V.A. 162-SW) Quadrangle; 2 miles south- 
west of Hall Crossroad, Fountain City (T.V.A. 146-SW) Quadrangle; Sally 
Cleveland Farm, 3 mile southwest of Washburn, Dutch Valley (T.V.A. 154-SE) 
Quadrangle ; 3 miles west-southwest of Thorn Hill, Avondale (T.V.A. 162-SW) 
Quadrangle; Maynardville Pike, 1.7 miles north-northeast of Hall Crossroad, 
Fountain City (T.V.A. 146-SW) Quadrangle; Raccoon Valley, 1 mile north of 
Wilson, Briceville (30’) Quadrangle. 
Lincolnshire formation in Virginia: At Speers Ferry, Clinchport (T.V.A. 
188-NW ) Quadrangle. 
Discussion—This species is similar to M. plicata from the closely related Lin- 
colnshire formation but does not have the strong fold and sulcus so characteris- 
tic of the Lincolnshire form. The shape and costellae help to separate M. semi- 
sulcata and M. quadrata. Furthermore, the pedicle muscle field of M. quadrata 
is much smaller than that of the other two species. 
MULTICOSTELLA SULCATA Cooper, new species 
Plate 71, A, figures 1-4 
Shell of moderate size for the genus; wider than long with rectangular cardi- 
nal extremities ; sides nearly straight ; anterior margin broadly rounded ; anterior 
commissure nearly rectimarginate despite a narrow fold and sulcus; costellate, 
costellae numbering 7 or 8 in 5 mm. at the front margin. Costellae with tendency 
toward fasciculation. 
Pedicle valve very gently convex in lateral profile; anterior profile very gently 
convex but with a narrow median hump; umbonal region slightly swollen ; 
median fold strong, subcarinate, narrow, extending from beak to anterior mar- 
gin. Flanks bounding fold depressed to gently concave; interarea moderately 
long, nearly catacline. 
Brachial valve gently convex and of about the same depth as the pedicle valve 
in lateral profile; anterior profile moderately convex with a deep and narrow 
median groove; sulcus strong, deep, narrow, extending from umbo to anterior 
margin. Flanks bounding sulcus forming narrow, strong plications; lateral 
slopes short and steep. Interarea short, anacline. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
ELOLGEY Be ot hb Sieh yeas. eleeaiers A Stopes 17.1 17.1 20.5-+ ? 6.7 
Paratype (pedicle valve) .... 16.9 r. 20.7 20.7 ? 
