PARTI CHAZYAN AND RELATED BRACHIOPODS—COOPER 973 
Type.—Holotype: 117297. 
Horizon and locality Edinburg formation (about middle of Nidulites zone) 
in Virginia: On Tumbling Run, 14 miles southwest of Strasburg, Strasburg 
(15’) Quadrangle. 
Discussion.—This is a small shell but a distinctive one. It is characterized by 
somewhat distant costellae which form indistinct and narrow fascicles. The pedi- 
cle valve is somewhat narrowly convex in anterior profile, and the sulcus on the 
brachial valve is deep. It differs from P. catawbensis in ornamentation and form; 
it differs from P. fasciculata and P. fascifera in its more distant costellae and 
finer fascicles ; it is not parallel sided like P. longa, and it differs from young 
forms of P. magna and ponderosa in its distant costellae and lesser fasciculation. 
It has a strong development of short, spiny projections particularly on the 
brachial valve. These were seen in other species but not in the degree to which 
they are developed on this one. 
PAURORTHIS sp. 1 
Plate 150, C, figures 25-37 
Shell of about medium size for the genus, subcircular in outline; relation of 
length and width variable, some specimens having width greater than length and 
vice versa. Greatest width at about the middle; margins strongly rounded; an- 
terior commissure gently sulcate. Surface fascicostellate; fascicles narrow, nu- 
merous, and consisting of 3 or 4 costellae. 
Pedicle valve unevenly convex in lateral profile, with the maximum curvature 
just anterior to the umbo; anterior profile narrowly convex and with steep lat- 
teral slopes. Beak long; interarea curved, gently apsacline. Umbo swollen; 
median area just posterior to middle strongly swollen. Anterior moderately 
swollen ; lateral slopes flat and steep. 
Brachial valve with maximum convexity just posterior to the middle; anterior 
profile broadly convex and with the median region slightly indented by the sul- 
cus. Beak prominent, umbo moderately swollen; sulcus originating at the beak, 
shallow and wide, merging anteriorly into the flattened anterior. Sulcus occupied 
anteriorly by 3 to 5 fascicles. Hanks gently swollen; lateral slopes steep. 
Interior of pedicle valve with deep notothyrial cavity; dental plates obsolete. 
Vascula media prominent and separated anteriorly by a short, low thickening of 
the floor ; diductor scars usually distinct, elongate, but often not impressed in old 
and thick shells. 
Brachial interior with thin cardinal process, thick brachiophores, and low 
median ridge. Adductor field deeply impressed, elongate. 
Measurements in mm.—1172992, length 9.8, brachial length 8.5, width 10.5, 
hinge width 7.4, thickness 5.7. 
Figured specimens.—117298a-e, 117299a. 
Horizon and locality—Basal Athens formation in Tennessee: 600 feet S. 40° 
E. of the railroad crossing 1 mile northeast of the courthouse in Athens, Athens 
(T.V.A. 125-NE) Quadrangle; roadside just east of intersection 24 miles south- 
southeast of Riceville, Calhoun (T.V.A. 125-SW) Quadrangle. 
