506 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
at about the middle; anterior profile narrowly convex in the midregion with long, 
flat, and steep slopes to the margins; anterior slope gently convex, long; beak 
somewhat elongated and protruding; umbo narrow, swollen, the swelling con- 
tinuing to the middle; umbonal slopes steep. Interarea gently curved, apsacline ; 
teeth small, pointed; fossettes deep; delthyrial cavity deep; dental plates short, 
divergent ; umbonal cavities shallow ; muscle field not deeply impressed, slightly 
thickened anteriorly. 
Brachial valve moderately convex in lateral profile and with the greatest con- 
vexity in the posterior third ; anterior profile broadly convex, indented medially, 
lateral slopes short, not steep. Fold originating at the umbo, widening anteriorly 
to the front margin where it is quite shallow; flanks bounding sulcus gently 
swollen ; slopes to posterolateral areas gentle. Notothyrial cavity deep, cardinal 
process a low, simple ridge; median ridge moderately high; brachiophores long 
and slender; brachiophore supports slender and discrete, fulcral plates well 
defined. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width ‘Thickness 
Holotype (pedicle valve)........... 10.5 i 12.2 9.1 3.1 
Paratype (lTr7 Gea?) o.'s.00'4 cae ree 8.6 7.4 9.5 7.1 3.9 
ia (pedicle valve 116903e)... 11.2 ? 12.3 10.3 3.1 
“ Os ET TOOORT).< ot Oly, ? 10.6 8.3 Fr 
4 (brachial valve 111788c).. ? 10.1 12.7 10.2 2.1 
% Cees jum LOGOS) sues 9.0 TZ 9.3 1.6 
Types.—Holotype: 116903c; figured paratypes: 111788a,c,e, 116903a,b,e; un- 
figured paratypes: 111788b,d, 116903¢,d,f-1. 
Horizon and locality —Chatham Hill formation in Virginia: 1.2 miles S. 31° E. 
of Sharon Springs, Burkes Garden (15’) Quadrangle. 
Discussion—This species is intermediate in size between S. kayi and S. per- 
plexa but differs strongly from both. From S. kayi it differs in having a more 
strongly sulcate brachial valve, and therefore a definitely sulcate anterior com- 
missure. It differs from S. perplexa in being a more robust shell, in having a 
more elongate beak and longer interarea, and having somewhat stronger costellae. 
SCAPHORTHIS sp. 1 
Plate 55, C, figures 27-29 
This is a large species as indicated by the four specimens available for study. 
These consist of a complete specimen, two brachial interiors, and part of a pedicle 
interior. The largest specimen is 10.8 mm. long and 13.0 mm. wide at the mid- 
dle. This is not as large as S. kayi nor is the species as convex or as strongly 
costellate as S. kayt. 
Figured specimen.—116908a. 
Horizon and locality.—Effna-Rich Valley formations in Virginia: At Porter- 
field Quarry, 5 miles east of Saltville, Maccrady (T.V.A. 218-NW) Quadrangle. 
