684 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
region gently swollen and the median region slightly more inflated. Sulcus shal- 
low, originating about one-third the length from the anterior margin, occupied 
by a low fold. Flanks moderately convex, and with moderately steep slopes to 
the margins. 
Interior: Spire long, with long descending branches and a wide jugum ex- 
tending nearly horizontally between the descending branches at about the middle 
of the valve. Hinge plates triangular, small. 
Measurements in mm.— 
Length Width Thickness 
PROOUY DE” 5 ois Uae eas car ate nec Meena a eta te 4.9 4.7 3.4 
Poratype’ (ritassa) so eee ee ee eee ee eee 4.0 ar7 27 
ns (HEPA4BAI NOAA RE OLE 4.2 3.5 2.6 
He CraveaBh) Diba sleeves Potendld pide 4.0 3.6 2.5 
Types.—Holotype: 111433a; figured paratypes: 111435a-c, 111433b, 117248b ; 
measured paratype: 117248a. 
Horizon and locality—Wardell formation and Wardell part of the Dryden 
formation (Hesperorthis beds) in Tennessee: 0.3 mile southwest of Little Bar- 
ren Church, on old Tennessee Highway 33, 10 miles southwest of Tazewell in 
Powder Springs (T.V.A. 154-SW) Quadrangle; vicinity of Lone Mountain, 
Tazewell (T.V.A. 154-NE) Quadrangle; west side of the sharp loop on the 
road down Flint Creek, NW4 of the center subquad., Powder Springs (T.V.A. 
154-SW) Quadrangle; north of the Canyon of Gap Creek, Powell Valley, Ten- 
nessee grid 790250N, 2677730E, 14 miles west of Arthur, Cumberland Gap 
(T.V.A. 153-SW) Quadrangle ; 34 miles north of Ooltewah, Ooltewah (T.V.A. 
112-SE) Quadrangle; Evans Ferry, 4 mile north of Indian Creek, Howard 
Quarter (T.V.A. 162-NW) Quadrangle. 
Wardell formation in Virginia: At Lloyd Carter’s barn, 0.8 mile northeast of 
Rye Cove School, Clinchport (T.V.A. 188-NW) Quadrangle; quarry on Sta- 
tion Creek, 4 mile south of U. S. Highway 58, 2 miles east of Cumberland Gap, 
Wheeler (T.V.A. 153-SE) Quadrangle. 
Ridley formation in Georgia: On U. S. Highway 27, 1 mile north of Rock 
Spring, Nickajack Gap (T.V.A. 113-SW) Quadrangle; quarry on the west side 
of the road 14 miles south-southeast of Cove Church, 5 miles south of Chicka- 
mauga, Kensington (T.V.A. 106-SE) Quadrangle. 
Ridley formation in Tennessee: 14 miles southeast of Hembree Mill, Se- 
quatchie Valley, Pikeville Special (15’) Quadrangle. 
Lebanon formation in Tennessee: On U. S. Highway 70N opposite Fairview 
Service Station, 4 mile west of Rome, Smith County. 
Barnhart formation in Missouri: On the old road 1 mile north of Chicago 
Summer School Camp, NW1iSW3 sec. 32, T. 37 N., R. 9 E., Weingarten (15’) 
Quadrangle. 
Discussion.—Silicified specimens from the “Lowville” limestone of Georgia 
permit description and illustration of some features of the interior. The dental 
plates are well developed, flaring and extended along the side of the muscle field 
for a short distance. The teeth are moderately strong and have well-developed 
