PART I CHAZYAN AND RELATED BRACHIOPODS—-COOPER 761 
Brachial valve deeply concave with the greatest concavity at about the middle. 
Posterolateral areas concave; umbo concave; lateral and anterior portions 
strongly folded toward the brachial valve to form a deep cup of the valve. Chi- 
lidium large; interarea short and hypercline. 
Interior: Pedicle interior with deeply sunk muscle field, diductor scars long, 
straight, and divergent; pallial and genital marks strongly impressed. Brachial 
valve with moderately elevated adductor lobes, moderately strong median septum. 
Measurements in mm.— 
Brachial Surface Mid- Hinge Thick- 
Length length length width width ness Height 
HolotypeCu tee 9.0 6.1 15.0 10.5 11.7 2.9 5.8 
Paratype (11I1099a).... 9.3 7.0 15.0 9.0 10.0 3.0 6.0 
‘4 Crt7401a) «005 77 6.6 11.0 9.2 9.7 3.3 4.1 
Types——Holotype: 111099b; figured paratypes: 111087a-c, 111099a,c-f, 
117460a,b, 117461a,b, 117462; unfigured paratypes: 111087d, 111099g-k, 
117461c. 
Horizon and locality—Oranda formation in Virginia: 4 mile west of Stras- 
burg; just west of junction of Virginia Highways 617=910, and 777, about 
0.2 mile north of Green Mount Church, Broadway (15’) Quadrangle; Bowman 
Farm, 0.3 mile east of U. S. Highway 11, 1 mile southwest of Woodstock, Edin- 
burg (15’) Quadrangle; on Virginia Highway 55, 0.4 mile west of U. S. High- 
way 11, north edge of Strasburg, Strasburg (15’) Quadrangle; on U. S. High- 
way II, 4 mile south-southwest of Tumbling Run, southwest of Strasburg, 
Strasburg (15’) Quadrangle; 200 yards southeast on Virginia Highway 616, 
3-5 miles southwest of Mount Jackson, Mount Jackson (15’) Quadrangle; dam 
on Shenandoah River, 15 miles N. 61° E. of Edinburg, Edinburg (15’) Quad- 
rangle. 
Same formation in Pennslyvania: 1 mile northwest of Guilford Springs, 
25 miles southwest of Chambersburg, Chambersburg (15’) Quadrangle; 1 mile 
south of St. Thomas, Mercersburg (15’) Quadrangle. 
Rodman formation in Pennsylvania: At Bellefonte, Bellefonte (15’) Quad- 
rangle. 
Dark shale below Eureka quartzite in Nevada: On the north slope of hill 
8167 on Martins Ridge, Monitor Range, Roberts Mountains (1°) Quadrangle. 
Martinsburg formation (part with Brongniartella=Salona) in Virginia: On 
Virginia County Road 617=910, 0.15 mile north of Green Mount Church, 
Broadway (15’) Quadrangle. 
Discussion.—This species is characterized by its large size and strongly in- 
flated pedicle valve, thus differing markedly from B. virginiensis. The Oranda 
species seems to be less swollen than B. pisum and is usually wider along the 
hinge than that species. 
BILOBIA MUSCA (6pik) 
Plate 192, D, figures 21-24 
Specimens of this species are introduced for comparison with the Appalachian 
species. 
