206 
Kirtley F. Mather 
Composita transversa n. sp. 
Plate XIV, figures 
Description. Shell small, sub-oval in outline, wider than long, 
valves strongly convex, fold and sinus absent but anterior margin 
slightly depressed in its mesial portion. The dimensions of two 
nearly perfect individuals are : length, 10.5 mm., 8.9 mm. ; width, 
11.2 mm., 10.0 mm.; thickness, 7,2 mm., 5.6 mm. 
Pedicle valve with greatest convexity in the umbonal region, 
the surface curving abruptly toward the cardinal margin and 
less sharply toward the lateral and anterior margins except that 
the convexity may be suddenly increased near the margin by the 
thickening of the shell in old age ; mesial fold absent though in 
some specimens there is a faint mesial line which seems to be 
a character of the shell structure rather than a depression in 
the shell surface; the line of union of the two valves slightly 
curved downward over the middle third of the anterior margin ; 
beak somewhat prominent and strongly incurved over that of 
brachial valve, foramen small, sub-circular. 
Brachial valve equally as convex as pedicle, greatest curvature 
in the umbonal region and decreasing toward the lateral margins ; 
mesial fold absent but curvature of the valve corresponding to 
that of the anterior line of contact between the valves; beak 
not prominent, incurved beneath that of opposite valve, marginal 
thickening of shell same as in pedicle valve. 
Surface of both valves marked by concentric lines of growth, 
ordinarily somewhat elevated, especially toward the margins, 
crossed by radiating thread-like striae. 
Horizon and locality. Hale formation : East Mountain, Fay- 
etteville, Arkansas (Station 137). Brentwood limestone: Fay- 
etteville, Arkansas (Station 148). 
PELECYPODA 
SOLENOMYA CID^ 
Genus SOLENOMYA Lamarck 
Solenomya sp. 
Plate XV, figure 8. 
The genus Solenomya is represented in the Morrow collections 
by an imperfect right valve preserved as an internal cast with 
