PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 781 
SOWERBYELLA EXIMIA Cooper, new species 
Plate 204, C, figures 13-33; plate 205, B, figures 7, 8 
Large for the genus, length two-thirds the width; cardinal extremities varying 
from slightly alate to slightly obtuse; sides gently rounded, slightly oblique to 
nearly straight; anterior margin ranging from broadly rounded to somewhat 
truncated. Ornamentation of the same type as that of S. punctostriata, con- 
sisting of costellae of unequal size, from I to 5 fine costellae separated by stronger 
ones; about 30 costellae in 5 mm. at the front margin. Costellae beaded. Pos- 
terior margin of both valves with oblique wrinkles. 
Pedicle valve having an uneven lateral profile, the greatest convexity located 
just anterior to the umbo, anterior profile broadly triangular, the median crest 
somewhat narrowly rounded but the sides long and flat and dipping only mod- 
erately steeply. Umbonal region gently inflated; fold low, indistinct, extending 
from umbo to anterior margin but not clear in all specimens. Median region 
gently inflated. Interior with oval diductor patches and short median septum. 
Inner surface strongly papillose. No strong vascula media extending from diduc- 
tor scars. 
Brachial valve moderately concave, most concave in the umbonal and median 
regions, the concavity forming a sort of sulcus; flanks gently concave toward 
the median region but flattening laterally and anteriorly. Posterolateral extremi- 
ties flattened. Interior with large muscle field but with septa low and delicate, 
reaching a crest at about the middle of the valve. Inner surface papillose particu- 
larly the broad, gently sloping area anterior to the septa. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness Height 
Fl olotype') /scicic/ aks! =e 10.0 0.4 16.5 16.5 1.8 3.1 
Paratype (117492b).. 11.7 10.8 19.0 18.8 2.1 3.9 
* (117492c).. 11.5 10.6 16.7 16.0 2.4 3.5 
: (117492h).. 89 8.2 14.3 ? 14.6 1.7 3.0 
ef (117492j) .. 10.7 9.6 16.0 16.3 2.6 3.9 
. (117492k).. 8.4 7.9 13.4 14.6 2.2 35 
Types.—Holotype: 117492a; figured paratypes: 117492c,d,f,h,j,k,n,p; un- 
figured paratypes: 117492b,e,g,i,l,m,0,q,r. 
Horizon and locality—Oranda formation in Virginia: Just west of junction 
of Virginia County Highways 617=91!0 and 777, on 777, 4 mile north of Green 
Mount Church, Broadway (15’) Quadrangle. 
Martinsburg formation (part with Brongniartella=Salona) in Virginia: On 
Virginia County Highway 617=910, 0.15 miles north of Green Mount Church, 
Broadway (15’) Quadrangle. 
Discussion.—Large size, beaded costellae, and poorly differentiated costellae 
are features of this species. The shell is not so robust as S. curdsvillensis nor 
are its interiors as much thickened as those of the Kentucky species. Sowerbyella 
eximia does not attain as large a size as S. punctosiriata (Mathers), and its cos- 
