THOMPSON: Humboldtiana from Chihuahua and Texas
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Table 1. Humboldtiana presidii Pilsbry, 1939. Measurements in mm of the holotype (USNM 134160) and 10 specimens from San Carlos Tunnel, 2.5 mi. N of the Coal Mine Ranch House (UF 345497/8, UF 345500/2).
 H W AW AH Whorls H/W AW/W AH/H AW/AH
Holotype 23.1 28.4 14.9 18.1 3.7 0.81 0.52 0.78 0.82
San Carlos Tunnel 
Min 23.7 31.0 15.8 21.0 3.7 0.74 0.51 0.78 0.75
Max 29.1 34.3 18.9 23.5 4.1 0.85 0.55 0.89 0.86
Avg 26.1 32.7 17.38 21.9 3.9 0.80 0.53 0.84 0.79
SD 1.66 1.31 0.96 0.79 0.11 0.04 0.04 0.03 0.03
than twice the length of the penis. Internally it has four longitudinal folds. The penis retractor muscle is relatively stout, 16 mm long. It originates on the middle of the inner wall of lung midway back from mantle collar and inserts on the base of the epiphallus at the apex of the penis. The flagellum is very long, 86 mm in length, and is about eight times the combined length of the penis + epiphallus. It is lined internally with 6 longitudinal columns of papillae. The lower vagina bears four sub-equal dart-sacs, of which ds, is the largest and ds3 is the smallest. The dart-glands form a ring around the middle vagina slightly above the dart sacs. The spermathecal duct is very long. The combined length of the duct + the spermatheca is 78 mm. The spermathecal sac is elliptical. The spermathecal caecum is very short. It diverges from the duct at about 8 mm below the base of the sac. The distal part of the spermathecal duct including the spermatheca and the caecum encompass the prostate-uterus just below the albumen gland (Fig. 9). The albumen gland is reniform in shape, and is 19 mm long. The carrefour is completely imbedded within the albumen gland.
Type locality. Near the San Carlos Mine, Presidio County, Texas. Holotype: USNM 134160; collected by J. A. Singley. The San Carlos Mine is located within 300 meters north of the San Carlos Tunnel, which is cut through a granite ridge. The mine is about 2.5 miles (4 km) north of the Coal Mine Ranch House.
Distribution. Known only from Presidio County, Texas in the immediate vicinity of the Coal Mine Ranch. Pilsbry (1939) records the species from near San Carlos [mine], and from the Rim Rock Mountains, which in part forms the northeast boundary of the Coal Mine Ranch. Texas. Presidio Co.: W edge of Sierra Vieja Rim, Quemada Spring area, ca. 5.8 mi. E of Coal Mine Ranch House (3025.6'N, 10440.1 'W), 1700 m alt. (UF 354496/7, UF 354498/1); San Carlos Tunnel, ca. 2.5 mi.
N of Coal Mine Ranch House (3027.7 'N, 10444.2'W), 1280 m alt. (UF 354495/4, UF354497/10, UF 354500/2)
Habitat. Humboldtiana presidii occurs in one of the bleakest areas in Texas. At the San Carlos Tunnel it was found among granite tallus at the base of a high bluff. Along the east side of the ranch at the base of the Vieja Rim the snail was found in similar granite tallus. Both localities were sparsely vegetated with Opuntia, scattered grasses, shrubs, and occasional small juniper trees.
Remarks. Humboldtiana presidii was described as a subspecies of Humboldtiana hogeana (Martens, 1890). At the time H. presidii was described the soft anatomy of neither was known, and the embryonic sculpture of H. hogeana was incompletely described. Similar features of the postembryonic shells suggested a close relationship between the two taxa.
The glossy shell of Humboldtiana presidii differs from H. hogeana by having a nearly flat and perfectly smooth embryonic shell, and by completely lacking granulation on any of the following whorls. The lusterless shell of H. hogeana differs by having course transverse wrinkled striations on the embryonic whorls and granular sculpture on the second half-postembryonic whorl. The embryonic sculpture of H. hogeana places that species in the subgenus Clydonacme.
The anatomy of Humboldtiana presidii is characterized by having a short stout penis with a large verge internally. The penis terminates with a shorter epiphallus, which in turn has a very long flagellum. The genital atrium is very short and almost flush with the body wall. The very long spermathecal duct has a short caecum just below the spermatheca. The lower vagina has four sub-equal dart-sacs, in which ds, is conspicuously larger and ds, is the most reduced in size. The dart-glands are narrowly separated from the dart-sacs.
Among Texas species Humboldtiana presidii re-