416 



PROCEEDINGS OF THE ACADEMY OF 



[June, 



enlarged, the rest slender. The basal third or less is sheathed, the 

 sheath composed of firm, circular muscles. The papilla (fig. 1, pp.) 

 is cylindric, with a conic, glancUform end. The retractor muscle is 

 inserted on the epiphallus, which is nearly as long as the penis, and 

 bears a short flagellum. The vagina is about three-fourths as long 

 as the penis. In two individuals the organs measure, in mm. : 



Baboquivari Mountains, the types No. 111,549, A. N. S. P., from 

 Station 25, in the head of Thomas Canyon about half a mile from 

 Baboquivari Peak. Also at Station 23, at the northern bases of 

 crags at summit of the spur which divides Thomas Canyon. In 

 Sycamore Canyon, at Station 26, in a slide on the ridge of the head 

 branch, about 300 feet or more below the summit; Station 27, about 

 1,000 feet lower, near bed of canyon; Station 28, still lower, and 

 Station 31, further down the canyon, low on the south side. 



In Oro Fino Canyon it was taken at Station 21, at the foot of the 

 cliffs on north side of Mount Mildred, a conspicuous butte at the 

 southern side of the mouth of the canyon; also Station 22, among 

 low crags near the north side of the canyon. 



This is the common species of the Baboquivaris throughout the 

 short section of the range which we explored. It is distinguished by 

 having a larger aperture than any other Sonorella known. The 

 rather long penis with a strong basal sheath and a papilla of very 

 peculiar and characteristic shape are diagnostic of the soft anatomy, 

 and confirmed in a number of individuals from several stations. 



All of the stations are on the eastern watershed of the range. The 

 only collecting station on the western slope (24) had a quite different 

 Sonorella, *S. vespertina. 



The size is smaller in Oro Fino Canyon. At Station 22 the shells 

 are decidedly more solid and more opaque than the types. Height 

 12, diam. 18 mm. to height 13, diam. 19.5 mm.; 4| whorls. Soft 

 anatomy is typical. 



Specimens from high on the ridge near the head of Sycamore Can- 

 yon, Station 26, are also rather small, diam. 18 to 19.3 mm. Near 

 the bottom of the canyon, at Station 27, the shells measure 19 to 



