66 PROCEEDINGS OF THE ACADEMY OF [Feb., 
43, rather slowly widening to the last, which is nearly double the 
width of the preceding, and well rounded peripherally. The embryonic 
shell consists of 14 whorls; the apex is smoothish; then a radially 
wrinkled area follows to the end of the first half whorl; the next 
whorl has forwardly descending delicate threads on its outer or per- 
ipheral half, the inner half being irregularly, shallowly pitted and 
roughened. The succeeding neanic whorls are lightly striate obliquely 
and very slightly, minutely roughened. The last whorl descends 
rather deeply in front. The umbilicus is contained about 54 times in the 
diameter of the shell. : The aperture is very oblique, peristome expand- 
ed, the ends strongly converging, the columellar end dilated, slightly 
impinging on the umbilicus. 
Measurements of seven specimens were given in our former paper, 
with diameters of 15 to 17.8 mm. Sixty-nine adults taken in 1906 
have the following diameters: 
Diam ..an Mim. eee 15 15.5 15.8 16 LGsZ 16.3 
Nov ot shells. 247265 4 3 2 29 is x 
Dian anvwmm N, 16:55 16.7 16.8 17% 17238 18 
Nozroisshelis.:.220). cas 5 4 6 12 13 1 
About 84 per cent. are from 16 to 17 mm. in diameter, and the 
total range in diameter is only 3 mm.'* Otherwise variation is seen 
only to a very slight extent in the width and intensity of the band 
and in the degree of deflection at the aperture. 
Type locality.—Quartzite Hill, back of Dixon’s place, about a mile 
south of old Fort Bowie. It has been found nowhere else. 
The locality was wrongly given as ‘‘ Bowie’ in our former paper. 
Bowie is a station on the 8. P. Railway about 15 miles from Fort 
Bowie, and on the mesa where no snails live. Fort Bowie is now 
deserted, and only the roofless adobe buildings and the cemetery 
remain. 
Sonorella bowiensis was found only in one colony very limited in 
extent but prolific in individuals. This colony—the only place where 
we have ever found Sonorella in abundance—is in a small thicket of 
long-leaved scrub-oaks with some underbrush of service berries 
(Amelanchier sp.) under a low cliff, somewhat more than half way to 
18 The concentration around the diameters 16 and 17 mm. is partly due to 
the fact that all shells more than 15.8 and less than 16.2 were counted as 16, 
and similarly with 17, giving a wider range than with any intermediate measure- 
ments. 
