950 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
anterior margin strongly rounded; anterior commissure sulcate. Costellae num- 
bering 2 (rarely 3) to the millimeter at the front margin. 
Pedicle valve gently convex in lateral profile, with the maximum curvature 
just posterior to the middle and the front half to third somewhat flattened ; an- 
terior profile broadly triangular. Umbo narrowly convex, the convexity con- 
tinued to the front margin to form a low fold; flanks bounding fold flat in pro- 
file and sloping steeply to the margins. Beak long; interarea long, apsacline. 
Brachial valve most convex in the posterior half when seen in lateral profile, 
the front half flattened. Anterior profile forming 2 low mounds separated by a 
shallow depression. Sulcus deep and narrow, widening and becoming shallower 
toward the anterior margin. Flanks bounding sulcus moderately and somewhat 
narrowly swollen; lateral slopes low and gently sloping. 
Interiors as usual in the genus; the pedicle valve having short, flaring dental 
plates and the brachial valve with prominent parallel brachiophore supports. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Holotype hic. sraslsns ots 10.2 9.4 11.5 9.1 4.8 
Paratype (117362a).... 8.0 he 9.5 8.9 4.8 
sf (rrz362b ). 228) 7:8 7.3 9.2 8.3 3.4 
Types.—Holotype: 117362c; figured paratypes: 96362e, 117362a,b, 1173632, 
d,e,g. 
Horizon and locality —Curdsville formation in Tennessee: On Tennessee 
Highway 33, 54 miles northeast of Maynardville, Maynardville (T.V.A. 145-SE) 
Quadrangle ; $ mile north of Sill (now under Norris Lake), lat. 36°17’31”, long. 
83°53'55", White Hollow (T.V.A. 145-SW) Quadrangle. 
Same formation in Virginia: At Pennington Gap, Lee County. 
Discussion.—This species is characterized by a fairly robust form although it 
is not nearly so large a shell as D. sulcata. It has a wide hinge with gently obtuse 
cardinal extremities, fairly strong costellae, and a moderately deep sulcus. Dal- 
manella rara is most like D. crassicostellata but differs in its larger size, thicker 
contour, deeper sulcus and somewhat finer costellae. The species is also identi- 
fied on the type slab of Onniella fertilis (Ulrich). On the reverse side of this 
slab to that which is figured a number of brachial interiors appear which have 
the subparallel brachiophore plates united with the median ridge that so charac- 
terizes Dalmanella. The specimens are here referred to D. rara and have the 
same association with O. fertilis as occurs at the locality northeast of Maynard- 
ville. The same association was found in silicified material etched from Tren- 
ton limestone collected 4 mile north of the submerged settlement of Sill in the 
White Hollow (T.V.A. 145-SW) Quadrangle, Tenn. 
DALMANELLA SCULPTA Cooper, new species 
Plate 158, F, figures 34-46 
Shell of about medium size for the genus, subcircular in outline; hinge nar- 
row; sides and anterior margin strongly rounded; anterior commissure gently 
