316 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
row notothyrial cavity; short and stout brachiophores, no cardinal process, and 
large adductor field occupying a position on each side of the long and thick 
median ridge. Pallial marks present, an oblique channel appearing just outside 
the inner adductor scars and extending from the end of the brachiophores nearly 
to the front margin. 
Measurements in mm.—Holotype, length 3.0, brachial length 2.7, midwidth 
3.5, hinge width 3.1, thickness 1.8. 
Types.—Holotype: 116851d; figured paratypes: 116851a-c,e-j. 
Horizon and locality—Pratt Ferry formation (lower third) in Alabama: 0.2 
mile southeast of Pratt Ferry, Blocton (15’) Quadrangle. 
Discussion.—This species differs from N. delicatula Ulrich and Cooper from 
the Lévis boulders in being somewhat smaller, much deeper and more convex 
in lateral profile, and in having a rounder outline. Furthermore, the interior of 
N. tarda has much more strongly impressed muscle scars and pallial marks. 
Nothorthis tarda is abundant in the Pratt Ferry formation and can be obtained 
by etching this limestone in acetic acid. 
NOTHORTHIS TRANSVERSA Cooper, new species 
Plate 38, F, figures 41-58 
Shell small, rectangular in outline, with rounded sides and rounded postero- 
lateral extremities. Anterior commissure deeply sulcate. Surface marked by 
fine intercalated costellae, about 28 to 34 in number. 
Pedicle valve moderately convex in lateral profile, strongly arched and some- 
what narrowly rounded medially in anterior profile; median region and umbo 
strongly swollen, the swelling continued anteriorly to form a fold marked 
medianly by a strong costella extending from beak to margin; sides gently in- 
flated and sloping steeply to the lateral margins. 
Brachial valve moderately convex in lateral profile; broadly and gently con- 
vex in anterior profile; sulcus originating at the umbo, wide and deep and oc- 
cupying more than half the width at the front margin. Flanks bounding sulcus 
gently inflated and with gentle slopes. 
Measurements in mm.—Holotype, length 2.7, brachial length 2.4, midwidth 
3.4, hinge width 2.9, thickness 1.5. 
Types.—Holotype: 117986; figured paratypes: 117985a-e. 
Horizon and locality.—Pratt Ferry formation (lower third) in Alabama: 0.2 
mile southeast of Pratt Ferry, Blocton (15’) Quadrangle. 
Discussion.—This species differs from N. tarda in its more transverse outline. 
Genus NICOLELLA Reed, 1917 
Nicolella Reep, Trans. Roy. Soc. Edinburgh, vol. 51, pt. 4, p. 860, pl. 10, figs. 25-27, 1917.— 
ScHUCHERT and Cooper, Mem. Peabody Mus. Nat. Hist., vol. 4, pt. 1, p. 77, 1032. 
The features that distinguish Nicolella are not in themselves distinctive but 
as a combination are quite characteristic. The ornamentation generally consists 
of bold, strong angular costae with anterior bifurcations. The fine ornament 
