goo SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
steep sides; beak small, umbo swollen; median region strongly inflated ; anterior 
slope steep. Interarea moderately long and curved. Pseudodeltidium nearly 
obsolete. 
Brachial valve most deeply concave in the median region. Sides and anterior 
sloping steeply toward the middle; cardinal extremities deflected toward the 
pedicle valve. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness 
Holotype) yrratewlatnvatxaws - 35.5 33.0 38.4 32.2 8.0? 
Paratype (98200b).......... 50.3 46.2 51.4 41.0 11.4 
a (OR2006 5s aig ass Se 36.9 33.8 40.2 40.6 ? 
7 (ATZFOAD ) are sini" 65.6 60.0 72.6 71.0 16.4 
Types.—Holotype: 98200a; figured paratype: 98200c; unfigured paratypes: 
98200b, 117794a,b. 
Horizon and locality—Benbolt formation in Virginia: At Green Valley 
Church, 3 miles southeast of Lebanon, Brumley (T.V.A. 205-SE) Quadrangle; 
several localities in the vicinity of Rye Cove, Clinchport (T.V.A. 188-NW) 
Quadrangle. 
Discussion.—This is another gigantic form as large as M. magna, but it is 
represented in the collections by only a few specimens. Consequently, all the 
details for this species cannot be listed at the present time. It is characterized 
by strong convexity and has a deeply concave brachial valve. The cardinal ex- 
tremities are marked by small ears. The square outline and rotundity are charac- 
teristic. No other described species is so strongly rotund. It differs from 
M. magna in its greater depth, thicker body region, and squarer outline. A speci- 
men sectioned through the middle shows a thick marginal rim on the anterior 
margin of the brachial valve. This anterior marginal brim is one of the prime 
distinctions between Macrocoelia and Opikina, the latter being thickened at the 
place of geniculation and having a thin trail anterior to the rim. 
MACROCOELIA RUEDEMANNI (Salmon) 
Rafinesquina alternata RUEDEMANN (not Emmons), New York State Mus. Bull. 40, p. 16, 
pl. 2, fig. I, 1901. 
Opikina ruedemanni SALMON, Journ. Paleont., vol. 16, No. 5, p. 597, pl. 87, figs. 31-33, 1942. 
Types——Holotype: Columbia Univ. 25909; paratype: Columbia Univ. 25916. 
Horizon and locality.—Rysedorf conglomerate in New York: At Rysedorf 
Hill, near Albany. 
MACROCOELIA sp. 1 
This is a moderate-sized species, slightly wider than long as usual in the genus. 
Hinge wider than the midwidth and cardinal extremities pointed. Only pedicle 
valves are so far known ; consequently, no effort is made to describe the species. 
The lateral profile is moderately convex with the maximum convexity slightly 
anterior to the middle. The anterior profile is strongly domed. The umbo is 
swollen broadly but is not continued anteriorly as a fold. Lateral slopes and 
