1910] NATURAL SCIENCES OP PHILADELPHIA. 67 



the summit of Quartzite Hill, back of Dixon's place, shown at (1) in 

 the photographic reproduction below. The snails were under 

 small stones and dead leaves. The abundant shelter and food and 

 favorable northeastern slope apparently led to an unusual multi- 

 plication of individuals, but no environmental factor seems to account 

 for their very small size. We searched the neighboring Bull Hill 

 thoroughly for Sonorella, but without success. Probably a more 

 extended exploration would result in finding other colonies in the 

 Fort Bowie Valley. Bowie Mountain and Helen's Doom should be 

 examined. 



The single locality of S. bowiensis lies between the ranges of S. 

 bicipitis and S. optnta. 



Fig. 5. — Quartzite Peak and Bull Hill, from the ridge on east side of the creek, 

 looking across Dixon's place, showing type localities of Sonorella bowiensis 

 (1) and Holospira cionella (2). 



S. bowiensis differs from S. bicipitis by the rounded end of the penis- 

 papilla and the actually and comparatively longer penis, over half 

 the length of spermatheca and duct, though the shell is smaller. The 

 shell differs by its smaller size and the faintness or absence of white 

 bands bordering the chestnut zone. 



The living animal is slate color on head and back, sides of foot pale 

 blue, borders of the foot orange; liver brown. In alcohol the back is 

 slate, sides, tail and sole whitish. The sole has slightly darker lateral 

 areas marked off with faint grooves. The crop is long and smooth. 



I have figured the genitalia of a specimen (pi. IV, fig. 6) for com- 

 parison with that previously published. The well-developed penis 

 has a long basal sheath, the lower part of the penis itself being quite 



