PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER ggI 
PIONODEMA MINUSCULA Willard 
Plate 155, A, figures 1-10; plate 155,G, figures 32-42 
Pionodema minuscula Witvarp, Bull. Mus. Comp. Zool., Harvard Coll., vol. 68, No. 6, p. 275, 
pl. 2, fig. 3, 1928. 
Small for the genus, slightly wider than long ; hinge narrow; cardinal extremi- 
ties obtuse; sides and anterior margin gently rounded; anterior commissure 
broadly uniplicate in adults. Costellae fine, crowded, unequal in size, those on 
the fold and sulcus stronger than those on the flanks. Costellae in fold and sul- 
cus 2 or 3 in I mm.; on the flanks costellae number 4, rarely 5, to the millimeter 
at the front margin. 
Pedicle valve with uneven lateral profile, the posterior part convex but the an- 
terior quarter somewhat flattened ; anterior profile gently and broadly convex; 
beak slightly curved, somewhat erect ; umbo somewhat narrowly swollen; median 
region convex; lateral slopes short and fairly steep. Anterior quarter depressed 
gently to form a shallow sulcus. Interarea gently curved, apsacline. 
Brachial valve about equal to the pedicle valve in depth, fairly evenly and 
moderately convex in lateral profile. Anterior profile broadly and moderately 
convex. Umbo with a small sulcus; umbo and median region longitudinally 
swollen to form a poorly defined fold. Lateral slopes moderately long and gentle. 
Interior with small cardinal process and widely spaced, subparallel brachiophore 
supporting plates. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Holotype! wiack oes eis. <'s 12.3 11.8 137 8.8 7.0 
Hypotype (1173209a).. 11.6 10.8 127 8.7 6.9 
s (117329b).. 9.3 8.6 10.5 8.0 5.9 
Types.—Holotype: M.C.Z. 8610; figured hypotypes: Columbia Univ. 26405 
(1013)a-c; U.S.N.M. 117328, 117329a; measured hypotype: 117329b. 
Horizon and locality.—Lebanon formation in Tennessee: At Lebanon, Wil- 
son County; La Vergne, Rutherford County ; Columbia, Maury County ; Shelby- 
ville, Bedford County; U. S. Highway 241, 14 miles southwest of Christiana, 
Rutherford County; U. S. Highway 41 at Mount Olivet, 10 miles southeast of 
Murfreesboro, Rutherford County; Wells Creek, Stewart County. 
Camp Nelson formation in Kentucky: At High Bridge and 3 miles south of 
High Bridge, Harrodsburg (30’) Quadrangle. 
Witten formation in Virginia and Tennessee: At many localities but speci- 
mens usually poor. 
Hatter formation (Hostler member) in Pennsylvania: At Waterside, Everett 
(15’) Quadrangle. 
Discussion—This species is distinguished by its generally small size, sub- 
quadrate outline, and fine costellae. It is thus like P. conradi but differs in its 
squarer form, in its fine costellae, and generally wider hinge. It differs from 
P. sulcata in its subquadrate rather than subcircular outline, finer costellae, and 
lack of the conspicuous sulcus on the brachial valve. 
