384 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
the inversion of the fold and sulcus. In young Eridorthis the pedicle valve pos- 
sesses a short fold and the brachial valve is sulcate, but in the adult a fold arises 
from the brachial sulcus and the pedicle valve becomes deeply sulcate. This is 
a common feature in many of the orthoid brachiopods. The presence of the 
strong fold and sulcus is a more important generic feature than the inversion. 
Hitherto Eridorthis has not been identified from rocks outside of Kentucky 
and the Ohio Valley. Its range was Trenton to Eden. The presence of a well- 
developed species of this genus in the Effna limestone is quite unexpected. 
ERIDORTHIS INEXPECTA Cooper, new species 
Plate 48, A, figures 1-6 
Shell large for the genus, superficially resembling Ovoplecia. Subrectangular 
in outline, wider than long, with narrowly rounded cardinal extremities. Lateral 
margins broadly rounded, anterior margin broadly rounded. Surface costellate, 
with 7 to 9 narrowly rounded costellae separated by spaces in width about equal 
to the width of the costellae; strong concentric lamellae undulate over the cos- 
tellae and are spaced about 4 to the millimeter. 
Pedicle valve unevenly convex in lateral profile with the most convexity in 
the posterior half, the anterior half being somewhat flattened. Beak broadly ob- 
tuse, extending slightly posterior to the posterior margin. Sulcus originating 
about 3 mm. anterior to the beak, widening gradually to occupy somewhat more 
than a third of the width at the front. Sulcus deepening anteriorly to form a 
short rounded tongue. Sulcus bounded by narrowly elevated folds raised above 
the flanks which are flattened to slightly concave and slope moderately steeply 
to the margins. Interarea fairly long, strongly apsacline, slightly curved, and 
with a narrow, open delthyrium. Musculature like Glyptorthis. 
Brachial valve moderately convex in lateral profile with the anterior third 
slightly more convex and the maximum convexity at about the middle. Anterior 
profile broadly convex. Umbo sulcate, sulcus shallow and short, becoming a fold 
between 3 and 4 mm. from the beak. Fold low and rounded but well differenti- 
ated from the flanks which are gently convex and fairly steep sided. 
Measurements in mm.— 
Length Width Thickness 
Holotype,.(pedicle: valve) ii..)55.5..03 cee! 15.7 19.7 3.2)¢ 
Paratype ( “ te TT TOLOOR:) cc sre einer & 15.3 17.8 4.1 
i. (brachial valve 110106e).......... 13.2 16.4 2.0 
Coa Ets STTOROOD)) eres eeve are 15.1 19.1 57 
" Gouss St Sprore6t) ieee 17.2 21.5 4.1 
- Gist oY PLITOLOO) oa. aetreee 10.9 14.3 2.3 
Types.—Holotype: 110104a; figured paratypes: 110106b-e; unfigured para- 
types: I10104b,c, 110106a,f,g. 
Horizon and locality.—Effna formation in Virginia: Porterfield Quarry, 5 
miles east of Saltville, Maccrady (T.V.A. 218-NW) Quadrangle ; Edinburg for- 
mation (Liberty Hall facies), 1.8 miles S. 4° W. of Bethel Church, 5.9 miles east 
of Harrisonburg, Harrisonburg (15’) Quadrangle. 
