Fauna of the Morrow Group 
191 
Kessler limestone: East Mountain, Fayetteville, Arkansas (Sta- 
tion 209). Morrow formation: near Wagoner (Station 294), 
Choteau (Station 298), and Ft. Gibson (Station 303), Okla- 
homa. 
Squamularia trans versa n. sp. 
Plate XII, figures 8-9a. 
Description. Shell large, transversely sub-elliptical in outline, 
length to width about as 3 to 4, greatest width at mid-length 
of valve, hinge-line a little over half as long as greatest width 
of valve. The dimensions of a nearly complete pedicle valve 
are : length, 24.4 mm. ; width, +32 mm. ; length of hinge-line, 
18.5 mm. ; convexity of valve, about 11 mm. ; height of cardinal 
area, 4.3 mm. Those of a complete brachial valve are: length, 
21.1 mm. ; width, 27.8 mm. ; convexity, about 7 mm. 
Pedicle valve strongly convex, the greatest convexity pos- 
terior to the mid-length of the valve, the surface curving 
abruptly from the elevated umbonal region toward the cardinal 
margin and more gently toward the lateral and anterior mar- 
gins, the mid-portion of the valve somewhat flattened anteriorly, 
the cardinal margins rounding narrowly into the lateral mar- 
gins which are scarcely defined and curve broadly into the 
anterior margin which has very little curvature in its mesial 
portion; beak full, strongly elevated and incurved above the 
large, open, triangular delthyrium which occupies the middle 
half of the cardinal area; area concave, with increasing curva- 
ture upward from the hinge-line, not sharply differentiated 
from the umbonal slopes which curve gracefully forward from 
its margins ; a very faint, broad, undefined, mesial sinus, always 
inconspicuous, is developed in some individuals anteriorly. 
Brachial valve less strongly convex than pedicle, its outlines 
the same, umbonal region much less elevated and consequently 
with less rapidly curving umbonal slopes; beak full, projected 
slightly beyond hinge-line, and incurved beneath that of oppo- 
site valve ; a broad, undefined, inconspicuous, mesial fold gen- 
erally developed anteriorly. 
Surface of both valves marked by concentric bands, whose 
width is quite variable but with typically about 12 in 5 mm., 
the bands squamose, imbricated one above the other and bearing 
