BART VE CHAZYAN AND RELATED BRACHIOPODS—COOPER 497 
205-SW) Quadrangle; north side of Highway 19, about 1 mile due north of 
Belfast Mills, Saltville (T.V.A. 212-NE) Quadrangle. 
Chatham Hill formation in Virginia: Virginia Highway 113, Marion-Chatham 
Hill road, 6 miles north of Marion, Chatham Hill (T.V.A. 218-NE) Quadrangle. 
Discussion.—This species is characterized by its angular outline, strong costae 
on the flanks bounding the fold, narrow and moderately deep sulcus, and low 
fold marked prominently by 1 costa stronger than the others in a fascicle num- 
bering about 5 costae. To compare with S. costatus see discussion under that 
species. It is suggestive of S. rectangulatus but differs in its less rectangular 
form, lesser length, and deeper, narrower sulcus. The ornamentation of S. con- 
vexus is not unlike that of S. mediocostatus, but the former species is more 
transverse and has a deeper sulcus. The form of S. obtusus is like that of the 
Benbolt species, but it has more numerous ribs, a hinge narrower than the great- 
est shell width, and a less deep sulcus. 
SKENIDIOIDES OBTUSUS Cooper, new species 
Plate 97, B, figures 13-18 
Shell of about medium size for the genus, wider than long; subrectangular in 
outline ; hinge as wide as, or slightly narrower than, the greatest width which is 
near the middle; cardinal extremities rounded, obtuse or nearly a right angle 
in the adult, auriculate in the young; sides rounded; anterior margin broadly 
rounded ; costae numbering Io or 11 on the flanks; narrowly rounded and with 
intercostal spaces about equal to the width of the costae; fold and sulcus marked 
by a number of costae varying from 5 to 9. 
Pedicle valve gently convex in lateral profile with the umbo somewhat more 
convex than the rest ; anterior profile subcarinate and strongly convex, the pedicle 
valve having great depth; fold low, best defined at the front; flanks gently 
swollen but with steep slopes to the margins. Interarea long, with large del- 
thyrium, strongly apsacline. 
Brachial valve slightly convex in lateral profile, nearly flat in anterior profile; 
sulcus only moderately deep but marked centrally by a narrow and deep trough 
corresponding to the median costa of the pedicle valve ; width of sulcus not equal 
to half the shell width. Flanks bounding sulcus gently swollen; posterolateral 
areas varying from gently convex to gently concave. 
Interior of pedicle valve with moderately deep free spondylium ; brachial in- 
terior with deep, wide, and long notothyrial chamber ; brachiophore plates low 
on median septum. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
lallagne, Mate Goren ie 3:3 3.0 4.5 4.2 2.2 
Paratype (117078c)..... 2.6 2.4 3.7 3.4 1.7 
Types.—Holotype: 117078a; figured paratype: 117078b, unfigured paratypes: 
117078c,d. 
