PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 581 
Type.—Holotype: 111160. 
Horizon and locality—Middle part of Arline formation in Tennessee: On 
north side of wagon road in cedar glade, 4 mile southeast of Friendsville, Con- 
cord (T.V.A. 138-SW) Quadrangle. 
Discussion.—This species is unlike any other Camerella known from the Appa- 
lachian region. It is characterized by the strongly arched umbonal region of the 
brachial valve so that the length of that shell is actually greater than that of the 
pedicle valve. In this respect the species resembles certain Canadian, Mystic, 
and Pogonip forms such as C. breviplicata Billings, C. arkansasensis (Ulrich 
and Cooper) and C. sublaevis (Ulrich and Cooper). It differs from all these in 
its possession of a broad fold having 6 costae, with 4 on the flanks. 
CAMERELLA TRIANGULATA Cooper, new species 
Plate 110, F, figures 22-35 
Shell of about medium size for the genus, greatest width in the anterior portion ; 
outline subtriangular; apical angle about 80°; length and width about equal; 
valves subequal in depth. Surface smooth except for strong costae in anterior 
third ; 2 costae in the sulcus, 3 on the fold, and 1 on the flanks. 
Pedicle valve moderately convex in lateral profile and with the maximum con- 
vexity slightly posterior to the middle; anterior profile broadly and gently con- 
vex ; umbo and median region swollen; sulcus originating at about the middle; 
sulcus wide and shallow. Tongue long, truncated on the front. 
Brachial valve unevenly convex in lateral profile, with the maximum convexity 
near the middle. Anterior profile strongly convex with steep sides. Umbo nar- 
rowly swollen ; median region inflated ; fold narrow, moderately elevated at front ; 
flanks narrowly rounded, terminating in a narrowly rounded lobe. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Lnlai ho) ra DR oe a ee ae 8.5 8.0 8.2 1.8 6.3 
CON ci viene eerie sig Ag acts 15.10 8.3 7.0 7.8 Hig 5.0 
Types.—Holotype: 111162; figured paratype: 117145. 
Horizon and localhity—Lenoir formation (shaly beds above Valcourea zone) 
in Tennessee: Billingsaria zone, $ and 1 mile northeast of Friendsville, Concord 
(T.V.A. 138-SW) Quadrangle; Knoxville; in front of church in center of 
Mosheim, Mosheim (T.V.A. 181-NW) Quadrangle; quarry on west side 
U. S. Highway 11, 14 miles southwest of Philadelphia, Philadelphia (T.V.A. 
131-NW) Quadrangle. 
Discussion —This species is characterized by its elongate-triangular outline 
and the few strong but short costae located at the front margin. It suggests 
C. varians of the Mingan and Crown Point formations but differs from that 
species in having a less convex brachial valve and much stronger costae at the 
front margin. No other Appalachian species is like this one. 
