972 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
east side of the road 0.2 mile north-northwest of Gooseneck, Louisville (T.V.A, 
138-SE) Quadrangle. 
Benbolt formation in Virginia: At Rye Cove, Clinchport (T.V.A. 188-NW) 
Quadrangle; 0.2 mile south of the middle fork of Moccasin Creek, 15 miles due 
south of Hansonville, Hansonville (T.V.A. 205-SW) Quadrangle; 4 mile east 
of Speers Ferry, Clinchport (T.V.A. 188-NW) Quadrangle; south side of 
Moccasin Creek, 1.2 miles east-northeast of Willow Spring, Hansonville (T.V.A. 
205-SW) Quadrangle; west slope of hill 4 mile east of Cedar Point School, Hil- 
ton (T.V.A. 197-NW) Quadrangle; south side of Mount Hagan School, Hilton 
(T.V.A. 197-NW) Quadrangle; east bank of sinkhole 300 feet south of Lake- 
view Church on Virginia Highway 71, southwest quarter east central subquad., 
Moll Creek (T.V.A. 196-SE) Quadrangle; on Virginia Highway 74, 53 miles 
east-northeast of the junction with U. S. Highway 54 (= Virginia Highway 71), 
Hilton (T.V.A. 197-NW) Quadrangle. 
Shippensburg formation (Pinesburg member-Echinosphaerites zone) in 
Maryland: On U. S. Highway 40 on the west side of Conococheague Creek, 
7 miles west of Hagerstown, Williamsport (15’) Quadrangle. 
Discussion—This is the largest species of this genus in the eastern United 
States. It is characterized by thick shells having a nearly circular outline or 
somewhat longer than wide. The fasciculation is strong but fine. The species 
differs from P. magna, the only other Paurorthis approaching P. ponderosa in 
size, by its stronger fasciculation, more circular form, and thick shells. Young 
specimens are also robust and subcircular. They are suggestive of P. catawbensis 
but are more robust. 
PAURORTHIS SPINOSA Cooper, new species 
Plate 151, E, figures 20-24 
Shell of about medium size for the genus, slightly wider than long, with 
rounded sides and anterior margin. Hinge narrower than the greatest shell 
width which is at the middle ; anterior commissure sulcate. Fascicostellate, fasci- 
cles narrow, generally consisting of 2 to 3 costellae. Costellae in median and 
anteromedian areas with short, spiny projections. 
Pedicle valve fairly evenly and strongly convex in lateral profile; anterior 
profile somewhat narrowly convex in the median region but with long, moder- 
ately steep slopes. Beak strongly incurved; interarea gently apsacline, strongly 
curved. Umbo narrowly swollen, the swelling passing anteriorly into the inflated 
median region. Flanks slightly convex in profile, moderately steeply inclined. 
Brachial valve fairly evenly and gently convex in lateral profile; anterior pro- 
file broadly and gently convex. Beak prominent, umbo swollen. Sulcus origi- 
nating at the beak, narrow and fairly deep at its place of origin but becoming 
wider and shallower anteriorly. Flanks moderately and narrowly swollen; lat- 
eral slopes short and moderately steep. 
Measurements in mm.—Holotype, length 8.5, brachial length 7.7, width 9.2, 
hinge width 7.0, thickness 5.4. 
