PART I CHAZYAN AND RELATED BRACHIOPODS—-COOPER 695 
near the middle; anterior narrowed and truncated; strongly sulcate; surface 
smooth. 
Pedicle valve strongly convex in lateral profile, with the maximum convexity 
anterior to the umbo; anterior profile narrowly convex and with steep, flattened 
lateral slopes. Beak narrow and strongly incurved; umbo narrowly rounded; 
median region narrowly rounded ; anterior region with low, narrow fold, flattened 
or depressed longitudinally by a more or less shallow depression extending from 
the anterior margin to the middle. Flanks flat or gently concave and steep. 
Brachial valve moderately convex in lateral profile, the posterior half fairly 
strongly convex but the anterior half bent strongly toward the pedicle valve. 
Anterior profile broadly sulcate. Umbonal region marked by a shallow, narrow 
sulcus which widens rapidly and deepens anteriorly. Flanks swollen and nar- 
rowly convex. Sulcus without inner fold except near anterior margin where it is 
more or less distinct. 
Measurements in mm.— Brachial 
Length length Width Thickness 
Ebolotype at bidet apr. ashi. sys 29)4-4 tastes 6.5 5:7 5.9 3.9 
Barina (W725 37) ous tects seine 6.6 5.5 5.8 4.0 
ot (CASES) sues Ait 6.9 6.1 6.5 4.2 
Types.—Holotype: 117253b; figured paratypes: 117253a,c. 
Horizon and locality—Edinburg formation (Lantz Mills facies) in Virginia: 
go feet above the Dinorthis transversa zone and go feet below the Oligorhynchia 
zone, 0.6 mile northwest of the junction of Virginia County Highways 616 and 
621, Richpatch, Eagle Rock (15’) Quadrangle. 
Discussion.—This species resembles C. bisulcata but does not attain the large 
size of the later Trenton species. Cyclospira bisulcata is a much more robust 
form and has a more prominent fold in the sulcus of the brachial valve. 
CYCLOSPIRA QUADRATA Cooper, new species 
Plate 141, A, figures 1-12; plate 143, B, figures 7-11 
Shell small for the genus, length and width about equal ; pentagonal in outline ; 
sides rounded ; greatest width at about the middle; shoulders prominent. Surface 
smooth. 
Pedicle valve fairly strongly convex in lateral profile; narrowly humped in 
anterior profile. Beak long, incurved; umbo somewhat inflated; median region 
narrowly convex; front with a poorly defined fold flattened on its surface. Flanks 
flat but sloping steeply to the margins. 
Brachial valve unevenly convex, the posterior half somewhat inflated but the 
anterior half extending toward the pedicle valve; anterior profile broadly and 
gently convex. Umbo and median region inflated; sulcus narrow and shallow at 
the posterior but broad and fairly deep anteriorly. Flanks moderately inflated. 
Measurements in mm.— 
Length Width Thickness 
EA GINIV DEEN. sit atebiee sc ssia 4 ele Slaves ne sie'e gr ecale 4.4 4.3 2.2 
Paratype CLT725OD) eiciceiin's seis ace nuek ee ees 4.2 4.1 2.4 
