292 



PROCEEDINGS OF THE ACADEMY OF [NoV.-DeC, 



Genitalia (Fig. 4a-(i). The penis is slender except at the base 

 where it is suddenly dilated. Internally there is a short, sinuous 

 fleshy fold and several minor folds in the dilated part of the penis 

 where it passes into the atrium, which also contains several fleshy 

 ridges. The papilla is long, slender and corrugated, Penial re- 

 tractor is terminal and enveloping base of the epiphallus, as usual. 

 The epiphallus is nearly as long as penis, with a slight distal swelling 

 in place of a flagellum. The vagina is shorter than the penis. Meas- 

 urements of the organs in mm. follow: 



The series of 60 specimens from Pima canyon consist chiefly of 

 dead shells. The average size appears to be slightly less in the 

 specimens from the western side of the canyon, forming the eastern 

 slope of Pusch Ridge. 



There are three "dead" specimens from "Pusa Ridge" (? = Pusch 

 Ridge) in the U. S. National Museum, No. 271,011, collected by 

 Barber. The diameter is about 22 mm. 



The specimens from the canyon north of Romero (opening north- 

 westward), Station 45 (1917), have the same range of variation 

 noted in Sabino canyon S. sahinoensis. There are depressed, more 

 openly umbilicate shells, together with smaller, usually less depressed 

 shells with relatively larger aperture and smaller umbilicus, I to 

 5 covered by the expansion of the columellarlip; also a few specimens 

 transitional in these characters. 14 examined. 



Alt. 15.4, diam. 27.3 mm., 4f whorls (largest). 

 " 15.6, " 23 " 4^ " 

 " 14.3 " 22 " (smallest). 



The genitalia do not differ from Pima canyon shells. 



Seven shells from Station 43 (1917) measure: diam. 21, 21.5, 

 23.5, 23.7, 24, 24.4, 24.4 mm. 



All of the localities for this form are in the arid lower zone of the 



range. 



Sonorella sabinoensis buehmanensis n. subsp. PI. V, figs. 2 to 36. 



Typically the shell differs from S. sahinoensis by being more solid 

 and more elevated, only very slightly paler near the shoulder band, 

 and with nearly one whorl more in examples of the same diameter. 



