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. auriculata 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- 

 soni, etc. 

 Polygyra texasiana (Moricand). PI. V, flgs. 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 (pi. 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 haxid. 

 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 texasiana or transitional between texasiana and 

 hyperolia in sculpture. At Del Rio, along the Rio San Filipe, Ferriss 

 and I found still the texasiana 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 



