I'Jlo J NATURAL SCIENCES OF PHILADELPHIA. 371 



Sonorella apache n- sp. Pi. VIII, figs. 2, 2a, 26. 



The shell is depressed, with low, conoidal spire, umbilicate (the 

 width of umbilicus contained nearly 9 times in the diameter of the 

 shell), extremely thin; mat isabella color above, paler below, glossy 

 and diaphanous in the central half of the base, encircled by a narrow 

 chestnut-brown band above the periphery. Whorls 4|, the embryonic 

 shell comprising 1|; sculptured like that of S. dragoonensis. The 

 neanic whorls are very minutely crinkled and closely set with short 

 bristles in irregular oblique lines. About 110 of these bristles stand 

 on one square millimeter, on the upper surface of the last whorl in 

 front of the aperture. The bristles are rather delicate on the last 

 whorl, and in cleaning the shell they are likely to be removed in 

 large part. The last whorl is wide and descends rather deeply in 

 front. The aperture is very oblique, subcircular. Peristome thin, 

 the upper and outer margins very narrowly expanding, basal margin 

 slightly recurved, colmnellar margin dilated, running forward. The 

 ends of the peristome converge strongly, and are connected by a 

 very thin, short, parietal film. 



Alt. 10.25, diam. 16.8, width of umbilicus 1.9, aperture 8.5 x 9.7 mm. 

 " 10 " 17 mm. 



Genitalia (PI. XI, figs. 5 to 5c). — The penis is short and very thick, 

 cylindric, obtuse at the ends, much shorter than the vagina. It 

 has very thin walls, and is filled by a thick, fleshy papilla (fig. 5a). 

 This is thick-walled with a rather large cavity having plicate walls 

 so that it is star-shaped in section (fig. 56). At the upper end of 

 its cavity there is a short, conic nipple (fig. 5c) ; at the distal end of 

 the papilla the cavity opens by a transverse slit. The retractor 

 muscle of the penis is inserted on the epiphallus near the penis. 

 The epiphallus passes imperceptibly into the vas deferens. There 

 is no flagellum. The lower end of the vagina is swollen, having 

 thick, fleshy walls. The organs measure as follows: Penis 7, 

 penis-papilla 5, retractor muscle 8, vagina 11 mm. 



Dragoon Mountains, the types from the southern or Cataract 

 branch of Tweed Canyon, at Station 9, on the east side of the rocky 

 bed near the foot of the "falls," No. 111,529. Also found at Station 

 1, a large slide of heavy, angular stone further north on the same 

 branch, rather high on the west side of the ravine, under the great 

 crag. A few dead shells were found at Station 27, in a gulch of the 

 rugged south wall of Tweed Canyon, and at Station 10, on the 

 eastern ridge of the amphitheatre of upper Tweed Canyon. 



