128 PROCEEDINGS OF THE ACADEMY OF [March, 
These structures form in their way a more perfect barrier perhaps 
than that produced by other means in P. awriculata and uvulifera. The 
species stands isolated at present. It is perhaps an aberrant and 
highly evolved relative of the Tennessee-Arkansas group of P. jack- 
sont, ete. 
Polygyra texasiana (Moricand). Pl. V, figs. 16, 17, 20. 
Specimens of typical P. texasiana were taken. by us in Hays, Comal 
and Bexar counties, Texas. Ferriss took it at Galveston. The type 
locality is ‘‘Texas.’’ In this widespread form the last two whorls 
are strongly rib-striate above, the riblets rapidly diminishing on pre- 
ceding whorls; the embryonic whorl is smooth and glossy. The ribs 
are strongest just behind the lip, and here continue upon the periphery 
or to the base, which is elsewhere nearly smooth or merely rippled. 
Fresh shells show a reddish peripheral band on the pale brownish- 
corneous surface. Specimens figured are from the west side of the 
Guadalupe river above New Braunfels, Texas. Alt. 5, diam. 11 mm. 
Along the Rio Grande P. texasiana occurs with transition forms to 
P. t. hyperolia. See below. 
Form with striate base. In some localities the ribs of the upper sur- 
face continue upon the base (pl. V, figs. 18, 19, Calhoun county, Texas), 
the other characters being unchanged. There are transitions to the 
normal sculpture of texasiana in some specimens, and we do not think 
it desirable to distinguish this form at present by a special name. Its 
distribution must be more fully worked out than we have been able to 
do. Calhoun county is on the Gulf coast near the southern angle of 
the State. 
P. texasiana hyperolia n. subsp. PI. V, figs. 13 14, 15. 
Shell more depressed than texasiana, glossy, very finely striate, almost 
smooth, above and below, with several riblets behind the lip-constriction. 
Uniform brownish-corneous or paler beneath, without a peripheral band. 
Aperture smaller and slightly more oblique than in texasiana. Alt. 4, 
diam. 9.3 to 10 mm. 
The type locality is the high land west of Devil’s river. This is the 
common Polygyra along the Rio Grande in Val Verde county, extend- 
ing north and northwest. The specimens from down the river, at 
Hidalgo, . . . . county, and Laredo, Webb county (collected by 
Singley), are either terasiana or transitional between texasiana and 
hyperolia in sculpture. At Del Rio, along the Rio San Filipe, Ferriss 
and I found still the terasiana and transition forms. 
On the high land west of the Devil’s river, Val Verde county, we 
found hyperolia in some numbers, under prostrate Yucca trunks and 
