16 
University of Texas Bulletin 
slightly forward, situated anteriorly; shell closed anteriorly, 
gaping posteriorly. Surface marked by lines of growth, which 
vary considerably in size. 
This shell resembles v. ry closely, II. vulgaris Shattuck, but 
differs from it in the curve of the dorsal and ventral margins, 
the expansion of the posterior, the greater proportional thickness 
of the shell, and the ornamentation. 
Locality. — Shoal Creek, Austin, Texas. From the top of the 
formation downward, about six feet. 
PACHYMYIDAE 
Genus PACHYMYA Sowerby. 
Pachymya austinensis var. budaensis n. var. 
PI. V; PL VI. 
Pachymya austinensis Shumard, 1859, Trans. Acad. Sci. St. 
Louis, Vol. I, pp. 604-605. 
Pachymya austinensis White, 1879, Eleventh Ann. Rept. U. S. 
Geol. and Geog. Surv. Terr., p. 298, PL 8, figs. 1, a, b; 
PL 5, figs. 7, a, b. 
I' achy my a austinensis Hill, 1889, Geol. Surv. Texas, Bull. No. 
4, P . 15. 
Pachymya austinensis Shattuck, 1902, U. S. Geol. Surv., Bull. 
205, p. 26. 
Dimensions. — Length, about 15cm.; breadth, about 9cm.; 
thickness, about 5.5cm. 
Description. — Shell large, heavy, gibbose; beaks anterior, in- 
curved, approximate; umbonal slope angulated from the beaks 
to the posterior extremity; anterior margin short, narrowly 
rounded; posterior margin truneate, narrowly rounded to angu- 
Iate below; ventral margin concave in the middle, more rounded 
anteriorly than posteriorly; dorsal margin nearly straight, sub- 
parallel to the ventral; sides, with a depression extending from 
below the beaks, obliquely backward and downward to the ven- 
tral margin; surface ornamented with strong, concentric lines 
of growth, crossed by granulate line radiating from the beaks. 
This shell is very closely related to P. austinensis Shum. and 
may be identical with it, but the Buda type is much higher pos- 
teriorly, and not so greatly angulated on the umbonal slope. 
Locality. — Shoal Creek, Austin, Texas. 
