PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 501 
sides nearly straight, sloping slightly medially ; anterolateral extremities some- 
what broadly rounded; anterior margin gently rounded to faintly emarginate. 
Anterior commissure deeply and widely sulcate. Surface costate, costae nar- 
rowly rounded ; intercostal spaces about equal to the width of the costae. Costae 
numbering about 24, with 10 in the broad sulcus and 3 marking the carinate 
part of the fold. Intercalation in 2 generations, 1 about a millimeter anterior to 
the beak and the other near midlength or somewhat anterior thereto. 
Pedicle valve deep but only gently convex in lateral profile; anterior profile 
strongly convex and narrowly rounded in the middle ; median region subcarinate ; 
fold not clearly demarcated from the flanks but the median fascicle consisting of 
a bifurcated pair, and the intercalated swollen costa intercalated in the pair is 
slightly elevated. Flanks flattened; lateral slopes steep. Interarea long and 
strongly apsacline ; beak prominent. 
Brachial valve faintly convex in lateral profile and broadly and gently convex 
in anterior profile. Umbo sulcate ; sulcus wide, deepening and widening anteriorly 
to occupy more than half the width at the front margin; flanks bounding sulcus 
perceptibly inflated, fairly narrow ; posterolateral extremities gently concave. 
Measurements in mm.—Holotype, length 3.8, brachial length 3.1, width 4.4, 
hinge width 4.8, thickness 2.3. 
Types.—Holotype: 117085c; unfigured paratypes: 117085a,b. 
Horizon and locality—Oranda formation in Virginia: Along the railroad 
4 mile west of Strasburg, Strasburg (15’) Quadrangle; 0.6 mile west of Linn- 
ville Station, Broadway (15’) Quadrangle. 
Same horizon in Pennsylvania: 1 mile north of Guilford Springs, 25 miles 
southwest of Chambersburg, Chambersburg (15’) Quadrangle. 
Discussion—tThis species is characterized by its squarish form, its cardinal 
extremities almost forming a right angle, broad and deep sulcus but broad and 
not strongly elevated fold. The species suggests S. elongatus to which it may 
actually be ancestral, but it does not have the extravagant development of that 
species. Its squarish outline will help to separate it from most of the other species 
described herein except S. obtusus. It differs from the latter in its wider hinge 
and stronger and more distant costae. 
SKENIDIOIDES TRANSVERSUS Cooper, new species 
Plate 98, C, figures 11-17 
Shell large for the genus, width approximately twice the length; cardinal ex- 
tremities acutely angular; sides gently rounded, sloping obliquely toward the 
middle; anterior margin nearly straight; anterior commissure sulcate; sulcus 
shallow. Surface costate, costae broad, rounded, low, and separated by narrow 
intercostal spaces. Costae numbering about 24. 
Pedicle valve evenly and gently convex in lateral profile; anterior profile 
broadly and fairly strongly convex; umbonal and median region moderately 
swollen ; fold inconspicuous, not elevated but forming the crest of the median 
swelling ; costae on fold 4 in number, consisting of 2 lateral costae extending to 
