546 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Types.—Holotype: M.C.Z. 8632; figured hypotypes: 117102a,b, 117105b, 
117106b-f, 117107, 117108; measured hypotype: 123296a. 
Horizon and locality.—Effna formation in Virginia: At the McNutt Quarry, 
12 miles southwest of Bland, Burkes Garden (15’) Quadrangle; Porterfield 
Quarry, 5 miles east of Saltville, Maccrady (T.V.A. 218-NW) Quadrangle; 1 
mile east of Tilson Mill, 16 miles northeast of Marion, Nebo (T.V.A. 223-NW) 
Quadrangle. 
Botetourt formation in Virginia: 1 to 2 miles northwest of Lexington, Lex- 
ington (15’) Quadrangle; Cedar Grove Church, 14 miles southeast of Harrison- 
burg, Harrisonburg (15’) Quadrangle; 4 miles east of Catawba, Salem (15’) 
Quadrangle; junction Virginia Highways 721 and 724, 2 miles northwest of 
Brownsburg, Lexington (15’) Quadrangle; 3 miles northeast of Blacksburg, 
Blacksburg (15’) Quadrangle. 
Basal Edinburg formation (Liberty Hall facies) in Virginia: On the boundary 
of George Washington Forest, 1.8 miles S. 4° W. of Bethel Church, 5.9 miles due 
east of Harrisonburg, Harrisonburg (15’) Quadrangle; 1 mile northwest of 
Lexington, Lexington (15’) Quadrangle. 
Whitesburg formation in Tennessee: Under the railroad bridge east of Bulls 
Gap, Bulls Gap (T.V.A. 171-SE) Quadrangle. 
Red Knobs formation in Tennessee: 3 miles east of Knoxville. 
Discussion—This species abundant in the Effna formation, is generally of 
small size and delicately costellate. It resembles O. gibbosa in form but is more 
delicately ornamentated and has less deep valves. It differs from O. parva in 
having a deeper brachial valve and finer ornamentation. Oxoplecia monitorensis 
is larger, has a wider sulcus, stronger costellae, and a more transverse outline. 
Oxoplecia holstonensis, like O. gibbosa, has variable ornamentation. This 
seems to be a matter of preservation, but it is difficult to be certain about the 
point. Some specimens appear to be nearly smooth, but the costellae are usually 
perceptible. In other specimens the costellae are well developed and strong, and 
the entire surface is covered by fila. The fact that fila are not visible on the 
smoother shells suggests that the ornamentation was worn away. This fact is 
confirmed by the common occurrence of this species in calcarenite matrix or 
lime-sands. This is an environment of rapidly moving water which would abrade 
the shell against the lime sand particles. 
OXOPLECIA MAGNAPLICATA Cooper, new species 
Plate 108, I, figures 43-48 
Large for the genus; outline rectangular with narrowly rounded cardinal ex- 
tremities, gently rounded sides, and somewhat narrowly rounded anterolateral 
extremities ; anterior margin straight. Hinge wide; strongly uniplicate; strongly 
costellate. Costellae irregular, thick and rounded, 6 to g on the flanks, 4 on the 
fold, 3 in the sulcus on the type, but with anterior intercalations more may be 
counted on other specimens. 
