PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 403 
sure broadly arched toward the brachial valve. Hinge width equal to about two- 
thirds the width. Brachial valve shallow. Pedicle valve flattened, giving the 
species a compressed appearance. Surface marked by simple, unbifurcated costae, 
about 36 in number. Interspaces generally wider than the width of the costae, 
which are narrowly rounded to subcarinate. 
Pedicle valve with narrowly swollen umbo occupying the posterior quarter 
and a prominent narrow beak ; posterolateral slopes nearly flat and broad, vary- 
ing to slightly convex where the cardinal extremities are bent toward the brachial 
valve. Median and anteromedian portions nearly flat to gently concave. Antero- 
lateral areas nearly flat. Interarea very short, varying from apsacline to nearly 
procline. 
Brachial valve moderately convex in lateral profile with the greatest convexity 
located in the posterior half; sulcus variable, when present originating at the beak 
and extending to the anterior margin where it is nearly merged in the general 
convexity. Sulcus usually occupied by 2 or 3 costae. Median half of valve gently 
swollen ; posterolateral slopes moderately steep; anterior slope gentle; cardinal 
extremities deflected slightly toward the brachial valve. Interarea apsacline, 
arched over pedicle valve interarea. 
Interior with pedicle muscle area small and brachial cardinalia delicate for such 
a large species. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
FEGOLY PE aks. oh geieiss 20.0 20.6 27.6 19.6 6.0 
Paratype (116981a).. 24.7 26.2 35.3 27.3 6.2 
9 (116981b).. 23.0 24.0 33.0 24.2 5.4 
Types.—Holotype: 116981c; figured paratypes: 116981a,b, 116982a, 116983b, 
c, 117988a; unfigured paratypes: 116981d, 116982b, 116983a, 117988b-e. 
Horizon and locality—Lincolnshire formation (Hogskin member) in Tennes- 
see: I mile southeast of Washburn, Dutch Valley (T.V.A. 154-SE) Quadrangle; 
10 miles north of Knoxville and 2 miles northeast of Hall Crossroad, Fountain 
City (T.V.A. 146-SW) Quadrangle; 1 mile north of Wilson Post Office, Brice- 
ville (30’) Quadrangle; 2 miles southwest of Hall Crossroad, northwest quarter 
center subquad., Fountain City (T.V.A. 146-SW) Quadrangle; Sally Cleve- 
land Farm, ? mile southwest of Washburn, Dutch Valley (T.V.A. 154-SE) 
Quadrangle; Evans Ferry, U. S. Highway 25F, # mile north of Indian Creek, 
Howard Quarter (T.V.A. 162-NW) Quadrangle; south of first bridge north of 
Thorn Hill, Avondale (T.V.A. 162-SW) Quadrangle ; southwest quarter of the 
northwest subquad; 0.4 mile east of Red Hill, Avondale (T.V.A. 162-SW) 
Quadrangle on road to Thorn Hill; 2.1 miles southwest of Mount Eager Church, 
Hogskin Valley, Powder Springs (T.V.A. 154-SW) Quadrangle. 
Same formation in Virginia: 1 mile west of Rye Cove; Speers Ferry; 4 mile 
northeast of Speers Ferry, Clinchport (T.V.A. 188-NW) Quadrangle; Lee 
Valley, Lee Valley (T.V.A. 171-NW) Quadrangle. 
Discussion—This species is distinguished by its large size and its direct un- 
