PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 977 
bundling of costellae. Lateral slopes of fold steep; flanks bounding fold flattened 
or gently concave, becoming gently convex in a posterolateral direction where 
the areas just anterior to the cardinal extremities are gently convex. Slopes to 
cardinal extremities gentle. Interarea short, apsacline. 
Brachial valve very gently convex with the greatest convexity in the posterior 
half ; about as deep as the pedicle valve. Sulcus narrow and deep in the posterior 
third, becoming wider and shallower anteriorly to the front margin where it 
occupies about one-quarter the valve width. Folds bounding sulcus strongest in 
the posterior, becoming flatter anteriorly and almost disappearing along the an- 
terolateral margin. Slopes to lateral margins gentle. 
Pedicle interior having small muscle field with width about equal to length; 
teeth small; dental plates short, stout. Median ridge inside the brachial valve 
heightened by the exterior sulcation which is most prominent at the posterior. 
Notothyrial cavity much restricted by secondary shell built on the inner sides 
of the short brachiophores; cardinal process short and stout. 
Measurements in mm.— 
Hinge Thick- 
Length Width width ness 
TOG EY ME a aici eee teal voc steestnuein ane orerarel troyorex ee SLO 31.8 32.3 ? 
Paratype (pedicle valve 110840m) ....... 13:3 17.8 17.3 ? 
oe Cress es WETOSAOE) he rerreteere 21.8 28.4 28.7 ? 
i uit St ULOSAC Aer ers ciate 27 Bg 27.3 Re 
n (brachial valve 110840k)....... 12.8 16.5 & ? 
z Ga? <: SeARROBAGH))i sites ieic 21.4 28.8 25.0? ? 
s (Cobie *) SETO840f)! + saeee 225.5 34.1 28.6 ? 
Types——Holotype: 110840b; figured paratypes: 110840a,c-g,i,w; unfigured 
paratypes: 110840h,j-v; figured specimens: 117346a-e. 
Horizon and locality Oranda formation in Virginia: 0.6 mile northwest of 
Linville Station; just west of the junction of Virginia County Highways 617= 
gio, and 777 about 4 mile north of Green Mount Church, Broadway (15’) 
Quadrangle. 
Bowman Farm, south side of U. S. Highway 11, 1 mile southwest of Wood- 
stock, Edinburg (15’) Quadrangle; Cedar Grove Church, 200 yards on Virginia 
County Road 616, 3.5 miles southwest of Mount Jackson, Mount Jackson (15') 
Quadrangle; on U. S. Highway 11, 14 to 2 miles southwest of Strasburg, Stras- 
burg (15’) Quadrangle; 3 miles north of Long Glade=Spring Hill, Parnassus 
(15’) Quadrangle. 
Same formation in Pennsylvania: 1 mile south of St. Thomas, Mercersburg 
(15’) Quadrangle. 
Jacksonburg formation in New Jersey: 14 miles south of Annandale, Hunter- 
don County. 
Discussion.—This species is characterized by its narrow fold and sulcus, large 
size, and fasciculate exterior. It is distinguished from R. edsoni in the less promi- 
nent development of the fold and sulcus. 
