396 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Hypotype (110302b)......... 14.1 14.3 18.9 14.8 5.7 
sf (#103022)! NUS 5 13.8 14.7 18.2 14.4 6.6 
(r10302c) te yet 8.8 8.8 re 9.5 3.8 
Types.—Holotype M.C.Z. 8595; figured hypotypes: 110301b-d, 110302a, 
110304d-g, 110309a; unfigured hypotypes: I1030I1a, 110302b,c, 1I10304a-c, 
I10309b-g. 
Horizon and locality.—Elway formation (blocky chert of Cooper and Prouty) 
in Tennessee: Along U. S. Highway 25W, 4.7 miles south of Clinton, Powell 
Station (T.V.A. 137-SE) Quadrangle; Evans Ferry section, on U. S. Highway 
25E about 1 mile north of Indian Creek, Howard Quarter (T.V.A. 162-NW) 
Quadrangle ; 4 mile northeast of Eidson, Kyles Ford (T.V.A. 170-SE) Quad- 
rangle. 
Elway formation (blocky chert of Cooper and Prouty) in Virginia: Speers 
Ferry, Clinchport (T.V.A. 188-NW) Quadrangle; on the road to Mountain 
Lake at the road fork, 4 mile north of the highway, at base of mountain, 14 miles 
northwest of Newport, Giles County; road cut on Route 64, 4 mile north of 
Dickensonville, Hansonville (T.V.A. 205-SW) Quadrangle; 1 mile north of 
Belfast Mills, Saltville (T.V.A. 212-NE) Quadrangle; on the road along Purga- 
tory Creek, 15 miles southwest of the Dunkard Church, 6 miles north of Bu- 
chanan, Natural Bridge (15’) Quadrangle; Sinking Creek in Giles County, Io 
miles north of Blacksburg; northwest side of knoll, 1 mile west of old Rosedale, 
Russell County; east of Moccasin Creek on Virginia County Road 679, 3 mile 
south of Tumbez, Moll Creek (T.V.A. 196-SE) Quadrangle; 1.2 miles south- 
west of Collierstown, Rockbridge County; road from Gate City to Hills Station, 
1 mile north of Copper Creek, Scott County. 
Whistle Creek formation in Virginia: Along Whistle Creek, 14 miles north- 
west of Lexington, Lexington (15’) Quadrangle; on Virginia County Road 602, 
53 miles S. 82° W. of Middlebrook, Augusta County. 
Discussion.—This species suggests a small variety of D. atavoides in general 
configuration of the valves but is smaller and less robust. In lateral profile the 
brachial valve of D. holdeni is not evenly convex, and the pedicle valve is gen- 
erally more concave anteriorly than is true of specimens of D. atavoides. The 
latter is also a proportionately wider species than D. holdeni. 
DINORTHIS INTERSTRIATA Willard 
Dinorthis pectinella Hatt (not Emmons), 2nd Ann. Rep. New York State Geol., pl. 34, 
figs. 39-40, 1883. HALL and CLARKE, Pal. New York, vol. 8, pt. 1, pl. 5, figs. 27, 28, 1893. 
D. interstriata WILLARD, Bull. Mus. Comp. Zool., Harvard Coll., vol. 68, No. 6, p. 270, 1928. 
This species is distinguished by its author from D. pectinella (Emmons) by 
the presence of a fine rib or costella between each pair of larger ones. The type 
specimen is from the Trenton of New York, but Willard identifies the species 
in the Virginia ‘“Ottosee.” It has not been identified in the National Collections. 
Type.—Holotype: A.M.N.H. 692 (larger specimen). 
