PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 881 
the beak and extending for about one-quarter the length where it is lost in the 
flat shell; remainder of valve nearly flat or very slightly concave. Interarea 
short. 
Interior of pedicle valve with short and shallow delthyrial cavity, short, thick 
teeth, short muscle field surrounded on each side by moderately strongly ele- 
vated thickenings. Diductor impressions separated by a low double ridge bear- 
ing the adductor impressions. Anterior and lateral third of shell strongly thick- 
ened and bounding a shallow visceral area. 
Brachial valve interior with slender brachiophores and delicate cardinal proc- 
ess. Median ridge short, wide and low; brachiophores supported by considerable 
thickening. Cardinal process consisting of two slender ridges. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Paratype CII7750d) svcicsas se 14.8 13.7 18.0 19.1 2.0? 
CII ZOOC) ss ccc ssnie 14.5 13.9 17.9 ? 1.4 
Types.—Holotype: 117759b; figured paratypes: 117759a,c-e, 117760a-d. 
Horizon and locality—Middle and upper Arline formation in Tennessee: 
Glade 4 mile southeast of Friendsville ; 100 yards southwest of Negro Cemetery, 
4 mile northeast of Friendsville, Concord (T.V.A. 138-SW) Quadrangle; 5 miles 
southeast of Knoxville; and 1,500 feet south of the mouth of Burnett Creek, 
Shooks Gap (T.V.A. 147-NE) Quadrangle; McMullens, Meadow (T.V.A. 
139-NW) Quadrangle. 
Discussion.—This species is compared with P. ? bellatula under the discussion 
of that species. No other species of the genus is now known. Platymena is 
common in the Arline formation in the Friendsville area. It occurs also in nodu- 
lar limestones of the contemporaneous Athens formation. 
GLYPTOMENA Cooper, new genus 
(Greek glyptos, engraved; mene, crescent) 
Shells generally subrectangular in outline, wider than long and attaining a 
width of an inch or more. Concavo-convex in profile; surface beautifully costel- 
late, larger costellae setting off groups of numerous finer costellae; whole sur- 
face crossed by fine fila. Pseudopunctae forming a dense mat. 
Pedicle valve with small, narrowly convex pseudodeltidium ; foramen present, 
minute. Interior with short, oblique dental plates with narrow umbonal cavities. 
Muscle field small, subcircular in outline and with the anterior ends of the diduc- 
tors separated by a low ridge. 
Brachial interior with narrow-lobed, short-shafted, bilobed cardinal process 
mounting a low notothyrial platform; brachiophores long, thin, flat, obliquely 
placed blades supported by swelling of notothyrial platform; median ridge short 
and low ; adductor scars small; adductor and accessory septa appearing as rem- 
nants only, usually absent. Subperipheral rim, low, not greatly thickened, usu- 
ally somewhat beaded. 
Genotype—Glyptomena sculpturata Cooper, new species. 
