PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 577 
CAMERELLA PLICATA (Schuchert and Cooper) 
Plate 114, A, figures 1-24 
Rhynchocamara plicata ScHUCHERT and Cooper, Amer. Journ. Sci., vol. 22, p. 248, 1931; 
Mem. Peabody Mus. Nat. Hist., vol. 4, pt. 1, p. 189, pl. 25, figs. 1, 2, 17, 18 (not 7), 1932. 
Shell of about medium size for the genus, somewhat triangular in outline, 
generally wider than long or with length and width nearly equal; greatest width 
about two-thirds the length from the beak. Angle formed by posterolateral mar- 
gins slightly less than a right angle; anterolateral extremities narrowly rounded ; 
front subtruncate. Posterior third to two-thirds of shell smooth, front half marked 
by narrowly rounded costae with interspaces about equal to width of costae, 2 oc- 
cupying the sulcus, 3 the fold, and 3 to 4 marking the flanks. An occasional 
extra costa appears in the sulcus and a corresponding one on the fold. 
Pedicle valve gently convex and with the maximum convexity in the posterior 
third. Sulcus originating at about the middle, shallow and occupying about half 
the width. Tongue short, truncated. Flanks slightly convex, slopes fairly steep. 
Median and umbonal parts slightly inflated. Spondylium long and deep. 
Brachial valve moderately convex in lateral profile, nearly semicircular in an- 
terior profile ; about twice as deep as the pedicle valve. Fold low, in some speci- 
mens scarcely distinguishable from the body of the shell. Flanks moderately 
convex and with steep slopes. Median part somewhat inflated. Cruralium short, 
shallow, and narrow. 
Measurements in mm.— 
Brachial 
Length length Width Thickness 
Fiynotype \GEUSIAZC) since. fies sitesi 10.8 10.0 10.9 8.3 
a GREASY ic. ia ctycinoiy tas see 10.6 10.0 10.7 7.9 
“ CEE TEAA) isso es osad yaidiecigee 10.5 9.9 10.5 7.7 
a (TIPT3O9))) A AS ee 90.5 9.0 10.4 VLE- 
Types.—Lectotype: Y.P.M. S2035 ; figured hypotypes : 111139d,g, I11147a-c; 
measured hypotypes: II11143a, 117144. 
Horizon and locality.—Ridley formation in Central Basin of Tennessee: At 
Nice’s (Ward’s) Mill, on Stone River, 8 miles (airline) northwest of Murfrees- 
boro; at Murfreesboro; Stone River Bridge on Tennessee Highway 96, 1 mile 
west of Murfreesboro; east side of Marshall Knobs, 5 miles south of Murfrees- 
boro; Rutherford County ; vicinity of Nashville, Nashville (15’) Quadrangle. 
Wardell formation in Tennessee: In the Hesperorthis zone on U. S. High- 
way 25E, 4 mile northeast of Indian Creek, Evans Ferry section, Howard Quar- 
ter (T.V.A. 162-NW) Quadrangle; 1.1 miles northeast of Lee Valley and at 
Lee Valley, Lee Valley (T.V.A. 171-NW) Quadrangle. 
Discussion.—This species is variable but in general consists of partially plicate 
forms having 2 costae in the sulcus and a length and width about equal. The 
species suggests the bicostate form of R. edmundsom but generally is not com- 
pletely costate as in that form. It is very suggestive of C. pennsylvanica but 
has fewer costae in the sulcus and has a more strongly convex brachial valve. 
