S10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
valve. The structure of the brachial valve is also quite different in spite of the 
fact that both have a high median septum. 
The closest similarity to Phragmorthis is to be seen in Mystrophora which is, 
however, a punctate genus. This genus also differs from Phragmorthis in hav- 
ing a plate in the delthyrium of the pedicle valve. In the brachial valve the two 
genera have similar septa, but the notothyrial cavity is shallower and more ele- 
vated on the septum than in Phragmorthis. Kayser describes the brachial proc- 
esses as short whereas those of the Ordovician genus are very long. 
PHRAGMORTHIS BUTTSI Cooper, new species 
Plate 146, D, figures 31-38; plate 148, B, figures 5-11; plate 148,C, figures 12-26; 
plate 221, C, figures 16-22 
Shell small, wider than long, strongly biconvex, with an elongate interarea on 
the pedicle valve. Hinge slightly narrower than the width at the middle. Cardi- 
nal extremities obtuse. Lateral margin rounded; anterior margin indented medi- 
ally. Anterior commissure sulcate. Surface ornamented by fine costellae, about 
4 in I mm. at the front. 
Pedicle valve moderately strongly convex in anterior and lateral profiles ; front 
emarginate ; valve swollen in the region from the beak to the anterior margin; 
lateral and posterolateral regions somewhat swollen. Midline of valve marked 
by a single costella stronger than the rest which extends from the beak to the 
indentation at the middle of the front margin and which serves as a fold. Con- 
centric growth lamellae bent posteriorly at this strong costella. 
Brachial valve strongly convex in lateral profile and with the greatest con- 
vexity at about the middle. Anterior profile bilobate. Valve divided into halves 
by a narrow groove extending from the beak to the anterior margin, this groove 
corresponding to the strong median costella of the pedicle valve. Flanks on each 
side of groove swollen. Lateral slopes moderately steep, and steeper than those 
to the median groove. 
Measurements in mm.—Holotype, length 5.9, brachial length 5.0, width 6.8, 
hinge width 6.2, thickness 4.2. 
Types—Holotype: 116959m; figured paratypes: 116947a-c,h,i, 116959b,d, 
h,k,l, 116960a-e,h,k ; unfigured paratypes: 116947d-g,j-l, 116958a-k, 116959a,c, 
e-g,i,j, 116960f,g,i,j. 
Horizon and locality —Effna-Rich Valley formations in Virginia: From Por- 
terfield Quarry, 5 miles east of Saltville, Maccrady (T.V.A. 218-NW) Quad- 
rangle; McNutt Quarry, 12 miles southwest of Bland, Burkes Garden (15’) 
Quadrangle. 
Edinburg formation (Liberty Hall facies) in Virginia: 1.8 miles S. 4° W. of 
Bethel Church, 5.9 miles west of Harrisonburg, Harrisonburg (15’) Quadrangle. 
Arline formation in Tennessee: On north side of wagon road in glade, 4 mile 
southeast of Friendsville, Concord (T.V.A. 138-SW) Quadrangle. 
Pratt Ferry formation in Alabama: On the road 0.2 mile southeast of Pratt 
Ferry, Blocton (15’) Quadrangle. 
Discussion.—This species is best recognized by its rotund valves, the elevated 
