408 



PROCEEDINGS OF THE ACADEMY OF 



[June, 



Alt. 11, diam. 19 mm.; aperture 9.9 x 11.25 mm. 

 " 11.3, " 19 " " 9.9x11 



" 10.8, " 18.8 " " 9.9x11 



" 10.3, " 18 " " 9.2x10.5 



" 10, " 17.8 " '' 9 X 10.3 



The most closely related species seems to be S. rowelli. This, 

 however, has a larger penis-papilla and a slightly wider umbilicus. 



The low and inconspicuous range Las Gijas (the Quartz Hills) 

 lies south of the well-known landmark Cerro Colorado, and west of 

 the northern end of the Tumacacori Range. At the northwest 

 end there is a mine, and a ranch building stands on the bank of a 

 small stream, the Gija Wash. The hill above the mine is strewn 

 with rounded boulders of coarse-grained granite, weathering to 

 angular gravel. Most of the loose rock is too massive to move, so 

 that suitable situations for snails are scarce. We found the first 

 Sonorellas on the slope above the mine. Working up over the 

 rounded top of the hill and along the ridge a half mile south we 

 crossed a low rock dyke, where a few more shells and a large colubrine 

 snake were taken. None were found among the rocks at the head 

 of the canyon east of this ridge. The other hills at this end of the 

 range are rounded, grassy, with little rock. On top there is much 

 sotol, ocotillo, a few cacti, etc. We found the pygmy Agave parvi- 

 flora here. It was not seen elsewhere. 



In the debris of the Gija Wash we found Thysanophora liornii 

 (Gabb), Zonitoides minuscula (Binn.) and Bifidaria pelleucida hor- 

 deaceUa (Pils.). 



Measurements of the genitalia of the preceding species are here 

 given together. The species identified as S. roivelli (Nc.) in these 

 Proceedings for 1905 being added for comparison. 



