142 PROCEEDINGS OF THE ACADEMY OF [March, 
At Derby, Frio county (pl. VII, figs. 20, 21, 22, 23, 24), the shells are 
bluish white with bluish streaks, a few brown tinted with brown 
streaks. The columellar tooth is small or wanting. This form has 
been called albidus Taylor, Ckll. 
At Laredo, Webb county (pl. VII, lower line of figs.), the shells are 
large and mostly long. The lot consists of pure white, and of coffee- 
tinted, brown-streaked shells, with all intermediate forms. A colu- 
mellar tooth is exceptionally developed. 
At Del Rio, Val Verde county (pl. VII, figs. 9,10, 11,12), we found a 
more conic race. The shells are white, often with some very faint 
grayish streaks. Interior varying from ochre-yellow to dark brown. 
In the series of about sixty living shells before us, none has mottled 
markings, and while in a few there is a weak indication of the colu- 
mellar tooth, it is as arule absent. The larger ones measure 29 to 33 
mm. long, 16 wide. Some of the dead shells found in the same place 
are larger, 35x 18.5 to 37x17 mm. A single albino was taken alive 
(fig. 12). These shells are from the plain along the San Filipe river, 
on the east side, not far from the Rio Grande. B. d. ragsdalei was 
found in the same place. 
On the mesa west of Devil’s river we found large dead shells like those 
from Del Rio but even larger, often with a low lump on the parietal 
wall, but no tooth on the columella. 39x 20.5 to 35x16 mm. 
At the Pecos High Bridge, on agaves, north of the railroad near the 
eastern end of the bridge, we found Bulimulus abundant and finely 
developed (pl. VII, figs. 1 to 7). The shape varies, but is always more 
conic than in the eastern localities. It is either nearly uniform white, 
or coffee-tinted varied with oblique brown or purplish streaks; these 
two color-forms in about equal numbers, found together on the same 
plants and connected by intermediate examples. Apex white. The 
interior is very dark purple-brown. The outer lip is usually but little 
thickened within, and the columella has no tooth, though often it 
is slightly salient in the middle. Whorls 7 to 7%. 
Alt. 36 37.0 33.0 34.5 36 83.3 937 jimm.: 
Diam. 19 kg) 17, 17 17) Ske Loss tok 
Aperture eset 8 , 16 16 16.1356 14.3 “ 
The last two measurements show the extremes of shape in a series of 
150 living specimens (No. 84,627 A. N.5.). 
Another set from east of the Pecos canyon about a mile from the 
Rio Grande is similar. The largest one measures, alt. 38, diam. 20.3, 
aperture 19 mm. (pl. VII, fig. 8). 
