498 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Horizon and locality—Edinburg formation (shale near middle of the Nidulites 
zone) in Virginia: 100 yards south of Battlefield Crystal Cavern entrance on 
U. S. Highway 11 at Hupp Hill, 1 mile north of Strasburg, Strasburg (15’) 
Quadrangle. 
Discussion.—The chief feature of this species is the narrow hinge, and in this 
respect it is unlike any of the others described herein except S. elongatus, but it 
is much smaller than that species. This species is like S. rectangulatus but differs 
in strength of costae and narrower hinge. 
SKENIDIOIDES OKLAHOMENSIS Cooper, new species 
Plate 97, A, figures 1-12; plate 08, E, figures 24-27 
Shell large for the genus, wider than long, with the width not quite twice the 
length. Cardinal extremities acutely angular; sides gently rounded, sloping 
obliquely toward the middle. Anterior margin narrowly rounded; anterior com- 
missure widely and deeply sulcate. Surface costate, costae numbering about 30 
on an adult; costae narrowly rounded; intercostal spaces narrower than the 
costae ; except for the fold, intercalations few and near the front margins. 
Pedicle valve deep, nearly flat in lateral profile in the young but gently convex 
in adults ; anterior profile broadly convex with median region somewhat carinate. 
Fold orginating at beak, marked by a complicated fascicle consisting of a thick- 
ened median costa on the side of which 2 or more costae are implanted. This 
median costa intercalated between 2 primary costae at beak. Flanks bounding 
sulcus gently convex and with moderate slopes to the sides ; interarea long, nearly 
catacline in the young, strongly apsacline in adults. 
Brachial valve unevenly convex in lateral profile, the posterior half nearly flat 
but the anterior half convex and bent strongly toward the pedicle valve ; anterior 
profile broadly convex; umbo flat; sulcus originating a fraction of a millimeter 
anterior to the umbo, widening and deepening anteriorly but with a deeper, nar- 
row track in the median part which corresponds to the thickened costa of the 
fold; sulcus occupied by 8 costae ; width of sulcus not quite equal to half the shell 
width. Flanks bounding sulcus narrowly and gently inflated; posterolateral 
extremities gently concave. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness 
EL OIOty Dey hemi cesiecs ocoaa 3.8 3.5 5.4 6.0 2.2 
Paratype (117079b)..... 4.0 3.5 4.6 5.6 2.5 
= CETZOZOC Y's ws: « 3.4 3.0 3.8 4.6 1.9 
ia (170700) eo... 2.6 2.6 4.4 5.0 T7 
Types.—Holotype: 117079a; figured paratypes: 117079d-f, 118007a-d; un- 
figured paratypes: 117079b,c, 118007e-¢g. 
Horizon and locality—Bromide formation (Mountain Lake member) 30 to 34 
feet below top of Decker’s bed 10 in Carter County, Okla.; On Tulip Creek, 
SWINW34NEI sec. 25, T. 2 S., R. 1. E.; north of the middle of sec. 32, T. 2 S., 
R. 2 E., 2 miles northeast of Springer. 
