forwardly descending threads, often visible only near the suture. Subsequent whorls have the usual fine growth-lines. The spire is rather small. The whorls increase slowly at first, the last one very wide, suture descending slightly in front. The aperture is rounded oval-lunate. Peristome is well expanded.
Fig. 162. Sonorella tortillita, type.
Height 15.3 mm., diameter 27.3 mm.; aperture alt. 14.7, width 15.9 mm.; 4-2/3 whorls.
Genitalia (Fig. 163). The penis is very long and rather slender, with muscular walls, containing a long, slender, corrugated, tapering verge. The epiphallus is shorter than the penis, without a distinct flagellum, though there seems to be a rudimentary one concealed in the integument. The penial retractor is long. Length of vagina is about equal to the penis. Length of penis 18, verge 8, epiphallus 11, vagina 17 mm.
Arizona: Tortillita Mountains, Pinal County (J. H. Ferriss), Type 118053 A.N.S.P., from east side of Hog Canyon; also found on the west side of same canyon near the cement dam, and south slope of mountains east of Hog Canyon. By the long penis and vagina this species resembles S. rinconensis, but in that snail these organs are far longer. S. santaritana is even more like S. tortillita in genitalia, but the shell is flatter, the whorls of smaller caliber. None of the Santa Catalina species has the vagina and penis nearly so long as in S. tortillita. The larger shells referred to (S. sabinoensis occidentalis are closely similar, but the threads of the embryonic whorl are better developed, the spire is wider, and the penis is only about half as long and differs by its swollen base.
The embryonic sculpture described is in large part effaced in the fully adult shells found. The color, too, is somewhat faded. In the young and barely full-grown examples it is decidedly darker than described. The largest specimen from the type locality measures 17.2 x 28.6 mm.; the
Fig. 163. Genitalia of Sonorella tortillita, with detail of the verge.
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