974 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Discussion.—The specimens described above suggest P. longa and P. fascicu- 
lata. They differ from the former in not having the strongly parallel sides and 
from the latter in not being so strongly fasciculate. They are nearer the latter, 
however. 
PAURORTHIS sp. 2 
Plate 151, B, figures 7-11 
Shell of about medium size, wider than long with narrowly rounded cardinal 
extremities, nearly straight sides and broadly rounded anterior margin. Anterior 
commissure somewhat narrowly sulcate. Surface fascicostellate, fascicles 
crowded, consisting generally of 2 or 3 costellae. 
Pedicle valve moderately convex in lateral profile and with the greatest curva- 
ture just anterior to the umbo; anterior profile narrowly convex in the middle, 
with long and moderately steep lateral slopes. Beak long, strongly incurved; 
interarea short, apsacline. Umbo subcarinate, the carination continued anteriorly 
as an indistinct fold nearly to the front margin. Lateral slopes slightly convex. 
Brachial valve gently and evenly convex in lateral profile; anterior profile 
gently and broadly convex and with the median region slightly depressed. Sul- 
cus originating at the beak, moderately deep and wide at the anterior margin. 
Flanks gently swollen; lateral slopes fairly long and gentle. | 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
RI AOsast peg ibe lehitela. y 8.0 7.4 9.0 m2 4.7 
TEGZOS enc a os isla iates 7.6 7.2 9.0 a2 4.3 
Figured specimen.—117302a; unfigured specimen: 117302b. 
Horizon and locality—Lower part of Sevier formation in Tennessee: 4 mile 
northeast of Miser, Louisville (T.V.A. 138-SE) Quadrangle. 
Discussion.—These shells suggest P. catawbensis in outline and the somewhat 
shouldered character of the posterior half. They are, however, more deeply sul- 
cate and have a more erect beak. 
CYCLOMYONIA Cooper, new genus 
(Greek kyklas, circle; mys, muscle) 
Shell small, dalmanellid in outline and profile; pedicle valve deeper than the 
brachial valve. Anterior commissure gently sulcate. Surface finely costellate, the 
costellae not markedly fasciculate. Punctate. 
Pedicle interior with small, long teeth ; dental plates fairly strong, receding and 
forming a rim to the muscle area. Delthyrial cavity deep, generally with the floor 
thickened and occupied by a wide adductor track; diductor scars small and nar- 
row. Anterior to delthyrial cavity floor of valve occupied by a short, elevated 
callosity. Vascula media strong, located on each side of callosity. 
Brachial valve like Paurorthis with small notothyrial chamber occupied by a 
simple cardinal process; fairly long brachiophores. Median ridge long and nar- 
row. Adductor field somewhat shield shaped, the posterior adductors lying out- 
