76 M ALONE JURASSIC FORMATION OF TEXAS. [bull. 266. 
Genus UNICARDIUM d'Orbigny. 
UnICARDIUM ? SEMIROTTTNDUM Sp. 11. 
PL XII. figs. 9-11. 
Shell thin, pyramido-suborbicular, moderately inequilateral, well 
inflated, the height nearly equal to the length; beaks large and prom- 
inent, pyramidal, submedian, placed a little nearer to the anterior 
than to the posterior extremity, curved inward and slightly forward, 
so that the anterior cardinal border is more concave than the pos- 
terior; anterior and posterior borders rather short; base evenly and 
rather broadly rounded; surface marked only with fine concentric 
growth lines, most of which are rather feebly, a few more strongly, 
impressed. 
Measurements. — Height, 21 mm.; length, 22 mm.; breadth, 13 mm. 
Height in another nearly like-proportioned example about 25 mm. 
Occurrence. — Twelve specimens were collected by Doctor Stanton 
at the following four localities: A mile and a half east of Malone 
station: ;mticline in east base of Malone Mountain about 1 mile north 
of its southern end; west of Malone Mountain, nearly 2 miles south 
of west from Malone station, in No. 13 of his Malone Mountain 
section; and in foothills at the northwestern end of Malone Mountain, 
a little over 2 miles east-southeast of Finlay station, here also appar- 
ently in Xo. 13. Four examples were also collected by me at the 
first of the localities above named. 
The species shows "some resemblance in form to U. varicosum, Sow- 
erby, but has larger and more elevated umbones and, for the body of 
the valves, a more rotund contour. 
UNICARDIUM ? TRANSVERSUM Sp. n. 
PI. XII, figs. 7, 8. 
Shell thin, well inflated, transversely subovate, the height equaling 
0.77 to 0.87 of the length; the posterior moiety of the shell nar- 
rower and considerably longer than the anterior, and the anterior 
part of the cardinal border more concave than the posterior; base 
broadly and unequally rounded; beaks prominent, yet less so than 
those of Unicardium semirotundum, in contact; surface smooth, 
marked only with fine concentric growth lines, which disappear under 
slight weathering. While the form of the shell is persistently trans- 
verse or subovate, the position of the beaks is widely variable, as 
shown by the umbonal fractions below, in which the numerator and 
denominator, respectively, denote the distances in millimeters of the 
umbonal summits from the anterior and posterior ends of the shell 
in four specimens selected at random. That this variability, how 7 - 
