THOMPSON: Humboldtiana from Chihuahua and Texas
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Table 2. Humboldtiana balanites n. sp. Measurements in mm of the holotype (UF 317170) and two paratypes (UF 317171,UF317172).
 H W AW AH Whorls H/W AW/W AH/H AW/AH
Holotype 30.9 33.1 19.0 24.3 4.2 0.93 0.57 0.79 0.78
UF317171 27.0 28.0 15.8 19.6 3.9 0.96 0.56 0.73 0.81
UF317172 28.0 30.3 16.8 21.6 4.0 0.92 0.55 0.77 0.78
tudinal folds. The lower vagina is very stout, and is slightly less than half the length of the penis. It bears four nearly equal sized dart-sacs, each of which has a bulge on either side of the base caused by the underlying dart-bulbs. The middle vagina is moderately long and bears four dart-glands that form a ring that is widely separated from the dart-sacs. The spermathecal duct is very long; about twice as long as the uterus-prostate. The spermathecal duct + spermatheca is 84 mm long. The bulbous spermatheca is 7 mm long. The spermathecal duct has a short slender caecum that diverges from the duct about a fourth of the distance below the spermatheca. The caecum is relatively short, 3 mm long.
Type locality. Chihuahua, 0.3 km north of San Ignacia Arareco, ca. 5 km south of Creel (2743.9' N, 10737.4'W); 2280 m alt. Holotype: UF 317170; collected 9 August, 2003 by Fred G. Thompson and Elizabeth L. Mihalcik. Paratype: UF 360035 (1) same data as the holotype.
The type locality is at the upper end of a small box canyon ending at a granite wall. Humboldtiana balanites was very sparse among dead oak leaves in an open forest of oak and pine at the upper end of a grassy pasture. Only two specimens were found after a two hour search. Apparently this species burrows into the soil to aestivate, because no dead shells or aestivation rings were found along rock ledges or in crevices.
Distribution. Known only from the type locality and a near-by locality. Chihuahua, 6.6 km E of San Ignacio Arareco, ca. 6 km south, 8 km east of Creel (2743.9' N, 10723.5' W), 2280 m alt. (UF 317171, UF 317172).
Remarks. Humboldtiana balanites is similar to H. durangoensis Solem, 1954. DNA sequences support this apparent relationship (Omar Mejia, personal communication). The latter two species are larger and have better defined bands. They also bear stronger granular sculptures. Humboldtiana durangoensis remains unknown anatomically. The spermathecal-duct
caecum in H. balanites is unusually short within the genus. Humboldtiana balanitesis is also similar to H. corruga Thompson & Mejia, 2006. Both species have rugosely wrinkled shells with fine granular sculpture over the postembryonic whorls. Humboldtiana balanites differs by having a narrower umbilical perforation, a weaker shoulder on the whorls, less inflated whorls, and less clearly demarcated bands. Anatomically H. balanites and H. corruga have similar large bulbous penises with an elongate verge surrounded by thick glandular folds. Humboldtiana corruga differs by having a much longer lower vagina and middle vagina, and a much shorter flagellum.
Among those species that are known anatomically, Humboldtiana balanites is similar to H. texana Pilsbry, 1927,, H. chisosensis Pilsbry, 1927, H. agavophila Pratt, 1971 and H.fullingtoni Cheatum, 1972, all from Texas, H. fasciata Burch & Thompson, 1957 from Hidalgo, H. globosa Burch & Thompson, 1957 from Veracruz, and H. corruga Thompson and Mejia, 2006 from Chihuahua. This group has in common a dart-gland ring that is widely separated from the dart-sacs, and the species have granular sculpture over part or most of the shell. Humboldtiana texana is similar to H balanites in color and sculpture, but it is much smaller, and the granular sculpture disappears on the last third whorl and on the base (Pilsbry, 1939: 404). Humboldtiana globosa differs from H. balanites by its brighter color patters, by its globose shape to the shell, and by having three functional, nearly equal-sized dart sacs, while ds4 is reduced in size. Humboldtiana fasciata differs from H. balanites by its larger size and more distinctly banded color pattern.
The commonality of the widely separated dart-glands and the dart-sacs may be a convergent character-state that does not necessarily reflect relationships. Humboldtiana fasciata and H. globosa are separated geographically from other species by great distances, and the brighter color patterns of their shells are quite unlike the drab patterns found in H. texana and H. balanites.