70 PROCEEDINGS OF THE ACADEMY OF [Feb., 



for recognition, or at least that it is difficult to decide upon some 

 specimens. Figures 1, 2, 3 represent specimens from Station 11, at 

 the foot of Reed's Mountain, Cave Creek Canyon. Figs. 4, 5 are from 

 about two miles up the south fork of Cave Creek. All of these are of 

 the form circumstriata. 



Fig. 6 is from Spring branch near Rucker Camp, head of Rucker 

 Canyon. This shell, and others from the head of Rucker, has a broad 

 conspicuous white border above the brown band, a narrower one 

 below it; the brown band is broader than in Cave Creek shells. The 

 spire, viewed from above, is narrower, the last whorl therefore 

 wider. 



Specimens from further down Rucker have much less conspicuous 

 white bordere along the band, and are like the type of virilis. 



This species also occurs in Morse Canyon, tne foot of Bonito Canyon, 

 and Shake Gulch, and in Horseshoe Canyon near the Red Box. 



In the Cave Creek Canyon Valley it may be found almost anywhere 

 suitable rock cover exists, though there are large areas without it, 

 where the slope is slight or with southern exposure. Rock "slides" 

 or northern exposures with abundant rock are its chief haunts. It 

 was taken at Stations 3, 4, 5, 1 1 , 12, 13, 14, also near the branch leading 

 toward Paradise, in the ravines west of Reed's Mountain, and various 

 places throughout the South Fork as far a^ explored — about two 

 miles up. None were taken on the great ridge where Stations 6 and 7 

 are situated, or on the ridge marked 10. The valley south of the 

 stream from the falls has not been explored. The Sonorellas were 

 also found in a great rock slide (trachyte?) on the south side of a peak 

 near the sawmill, in Barfoot Park, Station 1, and in the head of the 

 adjacent canyon running westward. See map on p. 107. 



S. inrilis (circumstriata) was found also in Paradise Canyon about 

 two miles below Paradise, and in Pine Canyon. 



Variation. — There is the usual variation in degree of elevation of 

 the spire, and slight variation in ground color of the shell, in all of the 

 lots examined, but various colonies differ in size, as may be seen by 

 the table of measurements of specimens from four places. This size 

 variation is not in the least correlated with elevation, but is invariably 

 connected with the exposure to the sun. Thus it will be noted that 

 at Stations 1 and 12 the mode is at 18 mm. diameter, the total range 

 from 16 to 20 mm. Both of these stations are on sunny southern 

 slopes, Station 1 being Barfoot Park at an elevation of over 8,000 feet, 

 while Station 12 is only about 100 feet above the bottom of Cave 



