890 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Trenton rafinesquinoids. On the inside of the pedicle valve the muscle field is 
large and broadly flabellate, and the pallial marks are deeply impressed. 
Inside the brachial valve interesting differences appear between Colaptomena 
and Rafinesquina sensu stricto. The cardinal process of Colaptomena is large 
and erect whereas that of Rafinesquina is of moderate size. In Colaptomena the 
adductor field is somewhat diamond shaped and moderately deeply impressed. 
No adductor ridges appear, but the field is bisected by a moderately long, low, 
rounded median ridge that extends posteriorly to the platform bearing the cardi- 
nal process. Another important feature of the genus is the reduction of the 
pseudodeltidium to disappearance. The pseudopunctae are coarse and densely 
matted together as in Opikina rather than distantly arranged in rows as in 
Rafinesquina. 
COLAPTOMENA LEPTOSTROPHOIDEA Cooper, new species 
Plate 267, A, figures 1-10 
Shell large, subquadrate to subrectangular in outline; slightly wider than 
long ; hinge variable, wider than the midwidth in the young, narrower than mid- 
width in old adults; cardinal extremities slightly alate and pointed to rounded 
obtuse ; sides subparallel; anterior margin somewhat narrowly rounded. Pedicle 
valve more strongly costellate than the brachial valve, 2 large and 2 small costellae 
at the front margin; brachial valve with 5 costellae in I mm. 
Pedicle valve perceptibly convex in lateral profile and with the umbonal region 
the most convex part; anterior profile broadly and gently convex. Umbonal 
region gently swollen, the swelling continuing noticeably to about the middle; 
remainder of valve nearly flat. Interarea short, only slightly longer than the 
brachial one. 
Brachial valve with umbo concave and posterior median region gently concave, 
rest of valve gently concave or nearly flat. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness Height 
FIGIOEY DE fo aiack «daveb ts 42.0 4I.I 40.0 ? 3.8 (Me Me 
Paratype (1177032)... ».- a7 ? 39.3 38.5 ? 3.0? 
. (£17703C)... 36.2 ? 41.3 35.8 ? 207 
ss (r17763a) 2% 19.3 ? 20.5 20.6 ? 1.3 
Types.—Holotype: 117761; figured paratypes: 117762a,c, 117763a,b,e; un- 
figured paratypes: 117762b, 117763¢c,d. 
Horizon and locality—Martinsburg formation (part with Brongniartella= 
Salona) in Virginia: County Road 617=910, 0.15 mile north of Green Mount 
Church, Broadway (15’) Quadrangle. 
Discussion.—No other species like this one is now known. 
MACROCOELIA Cooper, new genus 
(Greek macro, large; koilos, hollow) 
Shells large, attaining a width of more than 2 inches; subrectangular in out- 
line, usually wider than long; hinge variable; nearly planoconvex to strongly 
