Page:Land Mollusca of North America (north of Mexico) Vol. I Part 1 277-end.pdf/22

 This form is separated from S. sabinoensis solely on account of the difference in the penis, which is enlarged at the base in dispar, slender in sabinoensis. While the Pima Canyon shells are distinguishable from the large-mouthed typical forms of sabinoensis, we can find no difference in the sabinoensis with slightly smaller aperture, such as those from Sabino Canyon Station 9 (which agree in genitalia with the type of sabinoensis). No specimens with the penis swollen basally were found among the numerous Sabino Canyon individuals opened.

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. 271011, collected by Barber.

The diameter is about 22 mm.

The specimens from the canyon north of Romero (opening northwestward), Station 45 (1917), have the same range of variation noted in Sabino canyon S. sabinoensis. There are depressed, more openly umbilicate shells, together with smaller, usually less depressed shells with relatively larger aperture and smaller umbilicus, 1/3 to 1/2 covered by the expansion of the columellar lip; also a few specimens transitional in these characters. 14 examined.

Height 15.4 mm., diameter 27.3 mm.; 4-3/4 whorls. Largest.

Height 15.6 mm., diameter 23 mm.; 4-1/2 whorls.

Height 14.3 mm., diameter 22 mm. Smallest.

The genitalia do not differ from Pima Canyon shells.

Seven shells from Station 43 (1917) measure from 21 to 24.4 mm. in diameter.

All of the localities for dispar are in the arid lower zone of the range. (Dispar, different.)

Sonorella sabinoensis hesterna Pilsbry & Ferriss Fig. 166.

Sonorella hesterna Pilsbry & Ferriss, 1919, Proc. Acad. Nat. Sci. Phila., for 1918. p. 294, pl. 4, figs. 6-6b.

The shell resembles S. sabinoensis. It is rather solid, glossy, of the same dilute brown color, with distinct whitish bands on either side of the chestnut-brown band. Umbilicus 7 to 8-1/2 times in the diameter. Embryonic whorls with some radial rugosity, distinct below the suture, the threads interrupted into a fine, irregular and broken network, not recognizable as descending or ascending threads; this being the only definite difference from some forms of sabinoensis. Soft anatomy unknown, as only dead shells have been collected.

Height 14 mm., diameter 22.6 mm., aperture 11.5 x 12.6 mm.; 4-1/2 whorls Type.

Generated on 2012-11-05 12:13 GMT / http://hdl.handle.net/2027/uc1.31822013176466 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google