386 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
the width of a costella ; about 15 to 16 costellae on a valve. Lamellae strong, dis- 
tant, 3 or 4 in the space of I mm. 
Pedicle valve fairly strongly convex in both profiles and with the greatest con- 
vexity at about the middle; median costella more prominent and more elevated 
than those surrounding it; anterior end of median costella with a short costella 
implanted on each side to constitute an indistinct fold; median region swollen 
and with steep slopes to the margins, giving the valve as a whole a strongly 
inflated appearance. Interarea gently curved; apsacline. Pedicle interior with 
large teeth ; unbonal cavities filled; muscle field deeply impressed, adductor track 
long, thickened, and elevated. 
Brachial valve strongly convex in lateral profile with the greatest convexity in 
the umbonal region; broadly convex in anterior profile with the median region 
broadly indented by a low sulcus; umbo swollen ; sulcus originating at umbo and 
widening to anterior margin where it makes slightly less than half the width; 
sulcus occupied by 2 strong costellae; flanks bounding sulcus swollen; postero- 
lateral slopes steep. Brachial interior with stout curved brachiophores; short, 
thick median ridge and stout cardinal process. 
Measurements in mm.— 
Hinge 
Length Width width Thickness 
ELOLORY PEiya Fone cine &  Aeeeetee hia aS otb.s 5.0 5.8 5.8 3.7 
Paratype (pedicle valve 116955b)... 68 7.4 6.0 2.9 
< (brachial valve 116955a).. 5.9 73 6.3 2.0 
Type.—Holotype: 116955c; figured paratypes: 116954a-e, 116955a,b,d; un- 
figured paratypes: 116955e-h. 
Horizon and locality.—Arline formation in Tennessee: 100 yards southwest 
of the Negro cemetery, 4 mile northeast of Friendsville, Concord (T.V.A. 
138-SW) Quadrangle. 
Discussion.—This species is characterized by its globular form and the distant 
costation. The sulcus is wide and occupied by 2 costae. It is not like any of the 
other species herein assigned to this genus. It somewhat resembles Glyptorthis 
concinnula but is more strongly and distantly costate and the costae are less 
numerous. 
PTYCHOPLEURELLA GLYPTA Cooper, new species 
Plate 42, F, figures 28-39 
Fairly large for the genus, subrectangular in outline, wider than long; hinge 
slightly narrower than the shell width at the middle; sides gently rounded; an- 
terolateral extremities narrowly rounded; anterior margin truncated to emargi- 
nated ; anterior commissure rectimarginate. Surface marked by 17 strong, sub- 
angular costae; imbrications strong, 3 to the millimeter. 
Pedicle valve semiconical in lateral profile, the surface almost flat; anterior 
profile broadly and very gently convex ; umbonal region slightly swollen; median 
region of anterior half depressed to form a shallow sulcus; median costa promi- 
nent but depressed anteriorly below those surrounding it and shorter than the 
