PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 387 
others because it is in the reentrant of the emarginate anterior; sides bounding 
sulcus gently swollen; interarea long, almost catacline. 
Brachial valve fairly strongly convex in lateral profile ; anterior profile broadly 
and fairly strongly convex; umbo slightly inflated; median region somewhat 
swollen; umbo sulcate, sulcus deep and narrow, occupied by 2 costae; flanks 
bounding sulcus strongly swollen; lateral and posterolateral slopes steep. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Holotype "ii rsh aa. 5.9 5.9 8.0 7.0 4.4 
Paratype (116056b)..... 4.5 4.7 6.2 5.4 2.7 
‘s (116056c)..... 3.0 3.8 5.6 4.6 2.1 
Types——Holotype: 116956a; figured paratypes: 116956b,d; unfigured para- 
type: 116956c. 
Horizon and locality—Lenoir formation (calcarenites below Mosheim lime- 
stone) in Tennessee: On the southwest side of the cemetery behind Friends 
Church, north corner of Friendsville, Concord (T.V.A. 138-SW) Quadrangle. 
Discussion.—This species is abundant in a shaly bed in the sub-Mosheim cal- 
carenites at Friendsville. Interiors are rare; only the brachial one has been seen, 
and this presents no features unusual to the genus. Ptychopleurella glypta at- 
tains an unusually large size for the genus. In this respect it differs from the 
other species described herein. It is somewhat suggestive of P. porcia (Billings) 
but is more coarsely ornamented. 
PTYCHOPLEURELLA LAMELLOSA (Raymond) 
Plate 42, C, figure 12 
Orthidium lamellosum Raymonp, Amer. Journ. Sci., ser. 4, vol. 20, p. 371, 1905. 
Orthidium ? lamellosum Raymonp, Ann. Carnegie Mus., vol. 7, No. 2, p. 248, pl. 36, figs. 17, 
18, text fig. 24, IQII. 
Types.—Paratype: Y.P.M. 2706. 
Horizon and locality—Valcour formation in New York: Valcour Island, 
Plattsburg (15’) Quadrangle; Chazy, Rouses Point (15’) Quadrangle; and 
Crown Point, Port Henry (15’) Quadrangle. 
PTYCHOPLEURELLA MEDIOCOSTATA Cooper, new species 
Plate 42, E, figures 22-27 
Shell small, width nearly twice the length; cardinal extremities obtuse ; lateral 
margins narrowly rounded ; anterior margin deeply emarginate. Surface costate ; 
a strong and wide median costa occupying the center of the pedicle valve and 7 
or 8 costae marking the flanks. Interspaces V-shaped in section and about the 
same width as the costae. Entire surface covered by closely crowded concentric 
lamellae. 
Pedicle valve hemipyramidal in lateral profile with a nearly flat to slightly 
concave slope and catacline to strongly apsacline interarea. Anterior profile 
