PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 307 
ORTHAMBONITES MULTICOSTELLATUS Cooper, new species 
Plate 33, B, figures 4-7 
Shell of about medium size for the genus, wider than long and with gently 
convex sides and strongly rounded anterior margin. Cardinal extremities ap- 
proximately a right angle or slightly obtuse. Hinge equal to or slightly less than 
the width at the middle. Surface marked by about 36 narrowly rounded and 
closely spaced costae. 
Pedicle valve gently convex in lateral profile and with the greatest convexity 
in the umbonal region. Anterior profile swollen strongly in the middle and nar- 
rowly rounded; lateral slopes flat and steep. Umbonal slopes steep and concave ; 
umbo swollen and median portion inflated. Beak strongly incurved; interarea 
curved, apsacline. Teeth small. 
Brachial valve evenly and moderately convex in lateral profile; greatest con- 
vexity in the median region. Anterior profile evenly and broadly convex; 
umbonal region sulcate, sulcus small and disappearing in the general convexity 
of the valve near the middle. Median region swollen. Median ridge short; 
brachiophores short and stout ; cardinal process a simple ridge. Notothyrial plat- 
form thickened. 
Measurements in mm.— 
Length Width Thickness 
Holotype ‘(pedicle valve) oo... 0.00.00 10.9 TH7 4.4 
Paratype (brachial valve 116875a) ......... 14.4 15.6 ? 3.4 
e x5 Ler LOS7 SD) Seiad anne 10.9 14.2 FAG] 
Types.—Holotype: 116876a; figured paratypes: 116875a; unfigured para- 
types: 116875b-d, 116876b. 
Horizon and locality Edinburg formation (Cyrtonotella zone) in Virginia: 
Along the railroad about $ mile east of Strasburg Junction, Strasburg (15’) 
Quadrangle. 
Oranda formation in Virginia: Along railroad 4 mile west of Strasburg, Stras- 
burg (15’) Quadrangle. 
Discussion.—This species is characterized by its narrow and numerous costae 
and in this respect differs from all other Virginia species of Orthambonites 
described herein. 
ORTHAMBONITES NEUMANI Cooper, new species 
Plate 37, D, figures 15-28 
Shell large, rectangular in outline with the length equal to about four-fifths 
the width at the middle ; cardinal extremities acute ; sides slightly concave anterior 
to the cardinal extremities ; anterior margin broadly rounded; valves subequally 
convex; anterior commissure rectimarginate. Surface costate, costae rounded 
and separated by spaces of equal width to the costae, about 32 costae along the 
margin. Entire surface covered by fine concentric fila. 
Pedicle valve evenly and gently convex in lateral profile; anterior profile 
broadly and gently convex. Interarea moderately long, apsacline; beak small. 
