412 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
where the fold of the opposite valve is the strongest, and becomes shallower at 
the middle and front. At the front margin of an adult specimen the sulcus is 
exceedingly faint or absent. 
The surface of this species is finely multicostellate, but the costellae are of 
unequal size and appear in at least 3 generations by intercalation. 
Measurements in mm.—Holotype, length 12.0, brachial length 10.8, width 12.9, 
hinge width 11.8. 
Types.—Holotype: Carnegie Mus. 5450; figured paratypes: Carnegie Mus. 
5466, 5467, 5492. 
Horizon and locality——Crown Point formation in New York: Chazy, Rouses 
Point (15’) Quadrangle; Valcour Island and Crown Point, Plattsburg (15’) 
Quadrangle. Same formation in Vermont: At Fort Cassin, Port Henry (15) 
Quadrangle. 
Discussion.—The type specimens show this species to be a small form about 
one-third wider than long and with fine costellae covered by fine elevated fila. 
The brachial interior figured by Raymond (pl. 35, figs. 16, 18) and said to be- 
long to this species has the characters of Multicostella platys and is a larger 
and more coarsely costellate shell. 
Valcourea strophomenoides is characterized by its small size, somewhat rec- 
tangular outline, small muscle area, and shallow brachial valve. It differs from 
V. obscura in having less angular cardinal extremities, finer costellae, and a 
shorter, less prominent carina on the pedicle valve. 
VALCOUREA TENUIS Cooper, new species 
Plate 76, D, figures 18-29 
Shell of about medium size for the genus, wider than long, transverse in young 
stages; hinge forming the widest part; sides nearly straight, oblique; anterior 
margin broadly rounded. Anterior commissure rectimarginate. Surface costel- 
late, costellae separated by spaces about equal in width to the width of a costella; 
about 20 costellae in 5 mm. at the front margin. 
Pedicle valve gently concave in lateral profile, most concave in the median 
region ; fold low, originating at the beak and extending distinctly to a point near 
the middle; anterior to that point fold low and indistinct to the anterior margin. 
Flanks bounding fold gently concave ; posterolateral extremities flattened. Inter- 
area short, apsacline; pseudodeltidium short. Interior with muscle field not 
reaching the middle, subperipheral rim strong. 
Brachial valve gently convex in lateral profile; broadly and gently convex in 
anterior profile; sulcus deep, narrow, deeply entrenched in the posterior two- 
thirds, indistinctly defined in the anterior third ; flanks bounding sulcus narrowly 
but gently folded; posterolateral areas depressed, slopes short and gentle. In- 
terior with median ridge strongly defined nearly to the front margin; brachio- 
phores short, supported by callus; cardinal process with a long and stout shaft. 
